IMSA Signal Construction flashcards

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

Contract document order of precedence

When contract documents conflict, the stricter requirement usually governs. Typical rank is special provisions, then plans, then standard specifications, then standard drawings, but confirm the list printed in the actual contract.

MUTCD Standard versus Guidance

A Standard is a mandatory condition that must be met; Guidance is a recommended practice followed unless engineering judgment justifies otherwise; an Option is permissive. The word used in the text defines the obligation.

Plan scale verification

Never scale dimensions from a plan alone. Use printed dimensions and stationing, and treat the graphic scale as a check only. On a 1 inch = 20 feet sheet, one inch on paper equals 20 feet in the field.

Stationing arithmetic

One station equals 100 feet, so station 12+50 is 1,250 feet measured from the project baseline. Left and right offsets are measured perpendicular from that baseline, not from the curb line.

Primary signal face location

At least one primary signal face per approach is placed so drivers can see it between roughly 40 and 180 feet from the stop line at urban speeds, with greater distances where approach speeds are high.

Pedestrian clearance interval basis

Flashing DON'T WALK or countdown time is calculated from crossing distance divided by walking speed, commonly 3.5 feet per second, plus a startup allowance. Long crossings with refuge islands are timed by segment.

Push button distance from crosswalk

Accessible pedestrian push buttons are placed within about 5 feet of the crosswalk edge or curb ramp, on a level landing, so a user can press the button without leaving the sidewalk or entering the roadway.

Anchor bolt template use

A template holds the anchor bolts at the correct bolt circle, spacing, and projection while concrete is placed. Verify the pattern against the actual pole base before the pour; misplaced bolts cannot be fixed later.

Leveling nuts for pole plumbing

Leveling nuts below the base plate let crews plumb the pole after the foundation cures. The pole is then secured with top nuts torqued to specification, and the base gap is grouted or sealed per detail.

Utility locate before excavation

Call 811 and wait the state-required notice period before digging. Markings expire after a limited time and must be refreshed, and test holes are hand dug where signal conduit crosses marked utilities.

NEC 300.5 minimum cover

Direct-buried cable needs 24 inches of cover under streets, roads, and parking lots and 18 inches under residential driveways. Agency specifications often require deeper signal conduit, and the stricter requirement applies.

Straight pull box length rule

NEC 314.28 requires the box dimension along the direction of a straight pull to be at least eight times the trade size of the largest raceway entering it. Angle and U pulls use different multipliers.

Conduit fill forty percent

Where three or more conductors share a raceway, NEC Chapter 9 limits them to 40 percent of the conduit internal cross-sectional area. Two conductors allow 31 percent and a single conductor 53 percent.

Trench protection at five feet

OSHA requires a protective system such as sloping, benching, shoring, or a trench box for trenches 5 feet deep or more, plus competent person inspections, an exit within 25 feet, and spoil kept back from the edge.

Span wire sag and tension

Sag is set from the engineer's span chart, or tension is measured with a dynamometer, based on span length, wire size, and the weight and number of signals hanging on the span. Do not guess.

Mast arm capacity check

Confirm from the manufacturer's chart that the pole and arm are rated for the planned signals, signs, and luminaires at the design wind load before hanging anything, then torque anchor bolts to the specified value.

Secondary attachment for signals

Span-wire signals commonly require a safety chain or second attachment in addition to the primary clamp, so a single clamp failure cannot drop the head into the travel lane below.

Conductor color code signal

Agency wiring standards assign colors by function, commonly red for stop, yellow for caution, and green for the green indication, with a white or neutral common. Confirm against the color chart on the approved plan.

Cable tagging both ends

Label every cable and conductor at both ends with its phase, function, and destination before termination. Tags let testers fingerprint the wiring and let maintenance crews trace circuits without opening the whole cabinet.

Minimum cable bend radius

The manufacturer's datasheet controls, with limits commonly around 8 to 12 times the cable outside diameter. Tighter bends crack insulation and overstress strands, especially where cable enters a pull box.

Signal head height over roadway

The bottom of a vehicular signal housing over the roadway must be at least 15 feet above the pavement. Post-mounted heads on the side are set with the bottom at least 7 feet above the sidewalk.

Twelve-inch lens requirement

New vehicular signal installations normally use 12-inch lenses. Eight-inch lenses are generally limited to existing installations or low-speed conditions the MUTCD permits, and lens sizes are not mixed on one face.

Pedestrian signal mounting height

The bottom of a pedestrian signal housing is commonly at least 7 feet above the sidewalk and 10 feet above the roadway where it overhangs, so both pedestrians and vehicles clear it.

Countdown pedestrian signal

A countdown display shows the remaining crossing time during the flashing DON'T WALK interval. Current MUTCD practice requires countdown displays on new pedestrian signal installations, with display time matching the clearance interval.

Signal service dedicated circuit

A traffic signal controller is served by a dedicated, metered 120-volt AC circuit that supplies no other load, with a disconnect, overcurrent protection, and surge protection ahead of the cabinet.

Ground resistance twenty-five ohms

NEC 250.53 accepts a single ground rod with resistance of 25 ohms or less. Many transportation agencies require 5 or 10 ohms for signal cabinets, verified by fall-of-potential testing and recorded.

Inductive loop saw-cut depth

Loop wire sits in saw cuts commonly 2 to 3 inches deep and about 3/8 inch wide, sealed with backer rod and loop sealant. The turns are twisted together from the loop out to the lead-in cable.

Cabinet foundation above grade

The controller cabinet pad is typically set 6 to 12 inches above finished grade, with conduit sweeping up into the cabinet, so water drains away and the interior stays dry and accessible.

Insulation resistance megger test

A megohmmeter applies a DC voltage, commonly 500 volts, between conductors and ground. New signal wiring should read well above 10 megohms; low readings point to moisture, damaged insulation, or a nick in the jacket.

Flash before stop-and-go turn-on

New signals commonly operate in flashing mode for at least 24 hours, with advance public notice and notification to emergency services, before switching to stop-and-go so drivers adjust to the new signal.

Flagger certification

MUTCD Part 6 requires flaggers to be trained, and most states require a current certification card from a recognized program. Flaggers also need high-visibility apparel and a clear escape route.

High-visibility apparel class

ANSI/ISEA 107 Class 2 is the usual minimum for roadway workers in daylight. Class 3 is commonly required at night or where traffic speeds and sight distances are high.