IMSA Bench Tech II cheat sheet

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.

MUTCD signal indications are ranked: steady circular red stops traffic; flashing red is a stop-then-proceed; steady circular yellow warns of red and does not by itself prohibit entry if stopping cannot be done safely; flashing yellow means proceed with caution.

Signal head placement: at least one signal head per approach, with a minimum of two heads for through traffic on approaches where the speed limit exceeds 40 mph or where geometry limits visibility of a single head.

Yellow change interval formula: Y = t + v/(2a + 2gG), where t is driver reaction (typically 1.0 s), v is approach speed in ft/s, a is deceleration rate (about 10 ft/s²), and G is grade.

All-red clearance interval: AR = (W + L)/v, where W is the intersection width to clear, L is vehicle length, and v is approach speed; use it where crashes or queue spillback justify it.

Pedestrian clearance time: walk interval plus flashing DON'T WALK must allow a walking speed of 3.5 ft/s over the crossing distance, measured from the curb to the far curb or to the median.

Left-turn phasing: protected-only is used where permissive lefts produce crash patterns, where opposing speeds exceed 45 mph, or where there are two or more opposing through lanes with limited sight distance.

Preemption (fire, rail, emergency) takes priority over coordination; priority (transit signal priority) modifies splits and offsets within the coordination plan without terminating it.

Detector failure modes: a failed actuation detector typically leaves the phase resting in recall (max recall keeps the phase served every cycle; minimum recall serves only on demand).

Controller coordination parameters: cycle length, offset (seconds from sync reference to local zero), split (green plus yellow plus all-red per phase), and force-off points must sum to the cycle length.

MUTCD sign categories: regulatory (R) conveys laws and prohibitions; warning (W) alerts to conditions; guide (G) shows routes and destinations; services (blue), recreation/cultural (brown), and school (fluorescent yellow-green) have designated backgrounds.

Standard sign shapes carry meaning: octagon = stop, inverted triangle = yield, horizontal rectangle = guide or regulatory, diamond = warning, pentagon = school zone/crossing, circle = railroad advance warning, and X-crossbuck = railroad crossing.

Retroreflectivity: Type I sheeting is engineer grade, Type III is high intensity, Type IV is high intensity prismatic, and Types VIII/IX are microprismatic; minimum retroreflectivity must be maintained or the sign replaced.

Sign mounting height: rural post-mounted signs at least 5 ft above the near edge of pavement; urban post-mounted signs at least 7 ft; overhead signs at least 17 ft above the roadway.

Lateral placement: signs should be at least 6 ft from the edge of the travel lane in rural areas and 7 ft in urban areas where parking or pedestrians exist; minimum is 2 ft where constraints force it.

Pavement marking colors: yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction traffic and marks right edges and crosswalks.

Line patterns: a solid line discourages or prohibits crossing, a broken line permits crossing, and a double solid yellow line prohibits passing in both directions; a broken line beside a solid line permits passing only from the broken-line side.

Work zone and temporary markings: orange is reserved for temporary traffic control; raised pavement markers may supplement but generally do not replace markings on Interstates and freeways.

Illuminance (lux or footcandles) is light falling on a surface; luminance (cd/m²) is light reflected toward the driver. Roadway lighting design is normally specified in average maintained pavement luminance with uniformity ratios.

Luminaire mounting classifications: short mount up to 25 ft, medium 25-40 ft, and long over 40 ft; higher mounting yields wider spacing but lower vertical illuminance on the pavement near the pole.

Lamp types: high-pressure sodium is being phased out for new installations; LED is now standard for new roadway lighting because of efficacy, life, and dimming capability.

Pole spacing rule of thumb: spacing-to-mounting-height ratio typically runs 3:1 to 5:1 for cobra-head layouts; the actual ratio depends on luminaire distribution, wattage, and required uniformity.

Uniformity: average-to-minimum luminance ratio should generally be no greater than 3:1 to 6:1 depending on road class; poor uniformity produces bright/dark banding that impairs visibility.

Light trespass and glare control: full cut-off luminaires limit uplight and backlight; BUG ratings (backlight, uplight, glare) are used by IDA and many agencies to specify acceptable distributions.

Conflict with signals and signs: luminaires must not produce veiling glare on signal faces or wash out sign retroreflectivity; aim and shield fixtures near intersections and overhead signs.

Safety: de-energize and lock out the lighting circuit before servicing; verify with a meter, since photocells and time clocks can re-energize a circuit unexpectedly.

TTC zone components in order: advance warning area, transition area, activity area (including the buffer space and work space), and termination area.

Taper length formula for a lane closure: L = W × S for speeds of 40 mph or less, and L = W × S²/60 for speeds above 40 mph, where W is the offset width in feet and S is the speed limit in mph.

Buffer space separates traffic from workers; it should be at least the distance a vehicle travels in 2 seconds at the posted speed, and no work activity or equipment storage is allowed inside it.

Channelizing devices: cones, drums, barricades, and tubular markers; drums are preferred on freeways because of size and visibility, and spacing should not exceed the distance traveled in 2 seconds at the work zone speed.

Sign spacing in advance warning: the first warning sign is placed at a distance based on speed (roughly 100-350 ft for low speed, increasing to 1,000 ft or more on high-speed freeways), and successive signs follow at similar intervals.

Flagging: a flagger uses a STOP/SLOW paddle, wears ANSI/ISEA 107 Class 2 or 3 high-visibility apparel, and stands where approaching drivers can see them and where they can escape the path of errant vehicles.

Temporary traffic control devices must be crashworthy: they must meet NCHRP 350 or MASH acceptance criteria, and work zone speed limits should be posted only where justified by conditions.

Positive protection (temporary barrier, shadow vehicle with attenuator) is required where workers are exposed to traffic and where the work zone cannot be effectively separated by channelization alone.