IMSA Bench Tech II flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Yellow change interval

Duration between the end of green and the start of red. Computed as reaction time plus braking distance divided by approach speed, accounting for grade, so drivers can stop or clear safely.

All-red clearance interval

Period when all approaches show red. Length equals the distance from the stop line to the far edge of the conflicting traffic plus vehicle length, divided by approach speed.

Pedestrian walk speed

MUTCD design walking speed for pedestrian clearance is 3.5 feet per second. The flashing DON'T WALK interval must cover the crossing distance at that rate.

Protected left-turn phasing

A left-turn movement receiving a green arrow while opposing through traffic is stopped. Used where permissive lefts produce crashes, high speeds, or multiple opposing lanes.

Signal preemption

A control action that terminates the normal coordination plan to serve an emergency vehicle, train, or other priority call, then restores normal operation after the call clears.

Controller offset

The number of seconds between a system synchronization reference point and the start of local green for a coordinated phase; offsets create progression along an arterial.

Detector recall

A controller setting that calls a phase whether or not a vehicle is detected. Minimum recall serves the phase only when actuated; maximum recall serves it every cycle.

Flashing yellow arrow

A permissive left-turn indication meaning the driver may turn after yielding to opposing traffic and pedestrians; a steady yellow arrow or red follows to end the movement.

Stop sign shape

The octagon is reserved exclusively for STOP signs. No other sign uses this shape, which allows drivers to identify the sign by silhouette even when the legend is obscured.

Warning sign background

Most warning signs use a yellow diamond with black legend, except school and pedestrian-related warnings, which use fluorescent yellow-green for greater conspicuity.

Retroreflectivity types

Sheeting classes range from Type I engineer grade through Type III high intensity, Type IV high intensity prismatic, and Types VIII and IX microprismatic, with increasing brightness and durability.

Overhead sign height

Overhead signs should be mounted with a minimum clearance of 17 feet above the roadway, and post-mounted signs in urban areas at least 7 feet above the near pavement edge.

Sign lateral offset

Signs should be placed at least 6 feet from the travel lane edge in rural areas and 7 feet in urban areas with parking, with 2 feet as an absolute minimum.

Yellow pavement markings

Yellow lines separate traffic moving in opposite directions or mark the left edge of divided highways and ramps; white lines separate same-direction traffic and mark right edges.

Broken versus solid lines

A broken line permits crossing; a solid line discourages or prohibits it. Where a broken and solid line pair, passing is allowed only from the broken-line side.

Temporary marking color

Orange is the color reserved for temporary traffic control markings in work zones; standard yellow and white markings apply elsewhere on the roadway.

School zone sign color

School zone, school crossing, and school bus signs use fluorescent yellow-green backgrounds rather than standard yellow, making them more conspicuous in daylight and at dusk.

Illuminance versus luminance

Illuminance is light arriving at a surface, measured in lux or footcandles. Luminance is light reflected from that surface toward the observer, measured in candelas per square meter.

Luminaire mounting height classes

Short mount is up to 25 feet, medium mount is 25 to 40 feet, and long mount exceeds 40 feet; higher mounts allow wider spacing but reduce pavement illuminance near the pole.

Luminance uniformity ratio

The ratio of average to minimum maintained pavement luminance. Lower ratios mean more even lighting; poor uniformity creates bright and dark bands that impair driver visibility.

Full cut-off luminaire

A luminaire designed so no light is emitted above the horizontal, reducing skyglow and uplight. Backlight and glare are separately rated under the BUG system.

BUG rating

A three-part rating of backlight, uplight, and glare used to specify luminaire distributions. Higher numbers indicate more light behind the pole, upward, or at high angles.

LED roadway lighting

Light-emitting diode luminaires have largely replaced high-pressure sodium for new roadway lighting because of higher efficacy, longer life, instant restrike, and dimming capability.

Spacing-to-mounting-height ratio

The ratio of pole spacing to luminaire mounting height. For cobra-head layouts it typically falls between 3:1 and 5:1, depending on distribution, wattage, and uniformity requirements.

Lighting circuit lockout

Before servicing a roadway lighting circuit, de-energize at the breaker and apply a lockout tag; photocells or time clocks can otherwise re-energize the circuit unexpectedly.

TTC zone components

A work zone consists of the advance warning area, transition area, activity area with buffer space and work space, and termination area, arranged in that order along the roadway.

Taper length formula

For speeds of 40 mph or less, taper length equals offset width times speed. Above 40 mph, use width times speed squared divided by 60.

Buffer space

The unoccupied area between the transition and the work space. It provides a recovery zone for errant vehicles and should equal at least two seconds of travel at the posted speed.

Channelizing device spacing

Devices should be spaced so drivers pass no more than one per second; the spacing equals the distance traveled in two seconds at the work zone speed limit.

Flagger requirements

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 avoid errant vehicles.

Positive protection

Temporary concrete barrier, shadow vehicles with attenuators, or other devices that physically separate traffic from workers where channelization alone cannot provide adequate protection.

Crashworthy device criteria

Temporary traffic control devices must meet NCHRP 350 or MASH acceptance criteria so that when struck they deform in a predictable way and reduce injury to vehicle occupants.