IMSA Signal Construction cheat sheet

Conflict rule: when contract documents disagree, the stricter requirement normally governs. Typical precedence is contract special provisions, then plans, then standard specifications, then standard drawings - but read the precedence clause printed in that contract, because agencies vary.

MUTCD language sets the obligation: a Standard is mandatory, Guidance is a recommended practice to be followed unless engineering judgment justifies otherwise, and an Option is permissive. Note which word each paragraph uses.

In specifications, "shall" is mandatory, "should" is advisory, "may" is permissive. A pay item measured per linear foot of conduit in place usually includes fittings, sweeps, and pull tape unless the measurement section says otherwise.

Sheets: check match lines, revision clouds, and delta numbers against the revision block; the latest dated revision supersedes earlier sheets, and superseded details must not be built.

Stationing: one station equals 100 feet, so station 12+75 is 1,275 feet from the project baseline. Left and right offsets are measured perpendicular from that baseline, not from the curb.

Never scale dimensions from a plan alone. Use printed dimensions and stationing; treat the graphic scale as a check only, and verify disputed dimensions through an RFI rather than assuming.

Utility coordination: review the conflict matrix and subsurface utility engineering quality level before layout. Quality level B (designating) is not a substitute for test holes at conduit crossings.

Primary signal face: MUTCD practice places at least one primary face per approach so drivers can see it between roughly 40 and 180 feet from the stop line at urban speeds; higher approach speeds push the upper limit farther out.

Pedestrian clearance interval: flashing DON'T WALK or countdown time is based on crossing distance divided by walking speed, commonly 3.5 feet per second, plus a startup allowance where the MUTCD permits it.

Stop bar placement: the stop bar is set at or behind the near edge of the marked crosswalk; crosswalks are commonly 8 to 10 feet wide, with 6 feet as the usual minimum marking width.

Accessible route: each corner generally needs separate ramps aligned with each crosswalk direction, landing areas clear of the pole base, and push buttons within about 5 feet of the crosswalk edge.

Poles and cabinets are placed behind the curb and outside the clear zone where practical; check the recovery area for the design speed before fixing final pole locations on the staking plan.

Detector layout: stop-bar loops typically sit 4 to 6 feet upstream of the stop bar; advance loops are placed per the timing design and must not straddle lane lines or crosswalk markings.

Verify mast arm length and signal head positions against turning templates and sight triangles; a head that falls outside the driver's cone of vision at the stop bar will be treated as a supplemental face.

Call 811 before any excavation and wait the state-mandated notice period; markings expire, so refresh them if work is delayed. Hand-dig test holes where signal conduit crosses marked utilities.

Anchor bolts: set with a template that holds the bolt circle, spacing, and projection, and verify the pattern against the actual pole base before placing concrete. Misplaced bolts cannot be corrected after the pour.

Pole foundations are typically designed for the manufacturer's anchor bolt pattern and the governing wind load; confirm foundation elevation and top-of-concrete relative to finished grade before the pour.

Conduit stub-ups, sweeps, and pull string are placed in the foundation before concrete is placed; a foundation poured without the conduit is a demolition and replacement item.

Grounding: a ground rod and grounding electrode conductor, commonly bare copper sized per the plans, are installed with the foundation and brought into the pole handhole or cabinet.

Concrete is normally placed at the specified strength (often 3,000 to 4,000 psi) and poles are erected only after the cure or strength threshold in the specification is met - commonly around seven days.

Leveling nuts below the base plate allow plumbing after the foundation cures; final top-nut torque and grouting or sealing of the base gap follow the plan detail.

NEC 300.5 minimum cover: 24 inches under streets, roads, and parking lots for direct-buried cable, and 18 inches under residential driveways. Agency specifications frequently require 24 to 30 inches for signal conduit; the stricter applies.

NEC 314.28 pull box sizing: for a straight pull, the box dimension along the pull must be at least eight times the trade size of the largest raceway entering it. Angle and U pulls use different multipliers.

NEC Chapter 9 fill: 40 percent of conduit internal cross-sectional area for three or more conductors, 31 percent for two, 53 percent for one.

Bends: keep total bends between pull points at 360 degrees or less, use factory sweeps rather than field-made elbows, and install expansion fittings where conduit crosses structure joints.

OSHA trenching: at 5 feet deep or more, a protective system (sloping, benching, shoring, or trench box) is required, plus a competent person inspection, an exit within 25 feet for trenches 4 feet or deeper, and spoil kept back from the edge.

Separation: commonly 12 inches of horizontal and vertical clearance from water and gas mains, with greater clearance through casing crossings; verify against the utility owner's specification.

Prepare conduit before pulling: mandrel or swab each run, prove it with a pull tape, and cap or plug open ends so debris and water stay out until cable is installed.

Locate wire or detectable warning tape is installed above the conduit, commonly 6 to 12 inches, so future excavation locates the run before the bucket reaches it.

Span wire sag and tension come from the engineer's span chart or a dynamometer reading, based on span length, wire size, and the number and weight of signals, signs, and luminaires hanging on it.

A common messenger for signal spans is 3/8-inch 7-strand extra-high-strength galvanized strand; verify the actual size and grade against the plans, because span charts are size-specific.

Guy anchors are set so the guy opposes the span pull, commonly near a 45-degree angle, with turnbuckles and clips installed per the detail; guy wires do not substitute for adequate pole strength.

Mast arm and pole capacity: confirm from the manufacturer's chart that the assembly is rated for the planned attachments at the design wind load before hanging hardware, and torque anchor bolts to the specified value.

Plumb the pole on leveling nuts, tighten the top nuts, then grout or seal the base; check plumb in two directions after all attachments are hung, since added load changes the reading.

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

Overhead clearance for signal heads and signs is at least 15 feet above the pavement for the bottom of the housing; check clearance after tensioning, not before.

Color coding follows the agency wiring standard, commonly red for stop, yellow for caution, green for green, with white or neutral as common; confirm against the approved signal plan's color chart before terminating.

Tag every cable and conductor at both ends with phase and function before termination, so testers can fingerprint the wiring and maintenance crews can trace without pulling the cabinet apart.

Pulling tension is set by the cable manufacturer; hand pulling with a breakaway swivel is normal for 14 AWG signal cable, and lubrication is used where the run is long or has multiple bends.

No splices in conduit or inside the cabinet - splice only in pull boxes or handholes using listed connectors, and never rely on twist-and-tape.

Bend radius follows the datasheet, commonly around 8 to 12 times the cable outside diameter; tighter bends crack insulation and overstress strands at the pull box entry.

Terminations: strip to the specified length, use ferrules or listed lugs on stranded conductors, and torque terminal screws to the cabinet's torque schedule rather than guessing.

Separate signal and power conductors physically inside the cabinet per the plan, keep shields and drain wires bonded only at the end specified, and land the ground bus first.

Height: the bottom of a vehicular signal housing over the roadway is at least 15 feet above the pavement; a post-mounted head on the side of the road is set with the bottom at least 7 feet above the sidewalk.

Lens size: new vehicular installations normally use 12-inch lenses; 8-inch lenses are generally limited to existing installations or conditions the MUTCD permits, and lens sizes are not mixed on a single face.

Aim and orientation: each face is aimed parallel to the approaching lane and squared to the driver's view; backplates and retroreflective borders, where specified, go on before the head is hung.

Pedestrian signal heads: bottom of housing commonly at least 7 feet above the sidewalk and 10 feet above the roadway where it overhangs; the display is aligned to the crosswalk it controls.

Push buttons: mounting height commonly 36 to 42 inches above the sidewalk on a level landing within about 5 feet of the crosswalk edge, reachable without stepping into the street.

Accessible pedestrian signals require audible and vibrotactile output with locator tones; verify the volume and speech message at the actual intersection noise level, not just on the bench.

Signing: regulatory signs, DO NOT ENTER or ONE WAY placements, and overhead street name signs are checked against the plan sheet for size, position, and mounting height before turn-on.

Service: the controller cabinet receives a dedicated, metered 120-volt AC circuit serving no other load, with a disconnect, overcurrent protection, and surge protection ahead of the cabinet per plan and NEC.

Grounding: a grounding electrode and conductor per NEC 250; a single rod with 25 ohms or less is accepted by NEC, while many transportation agencies require 5 or 10 ohms, verified by fall-of-potential testing.

Cabinet pad: typically set 6 to 12 inches above finished grade so water drains away, with conduit sweeping up into the cabinet and the opening sealed against rodents and moisture.

Cabinet checks before energizing: door switch, fan and thermostat, heater, police panel, conflict monitor, and the controller model (NEMA TS 2 Type 1 or 2, 170, 2070, or ATC) match the plan.

Inductive loops: saw cuts commonly 2 to 3 inches deep and about 3/8 inch wide, filled with backer rod and loop sealant; the turns are twisted from the loop to the lead-in to limit pickup of adjacent fields.

Detection verification: measure loop inductance and resistance and compare to calculated values, run a presence and passage test per phase, and confirm video or radar zones with a test vehicle at night and in rain if required.

Power transfer coordination: schedule the utility connection and meter installation early, and confirm phase rotation and voltage at the cabinet before energizing the controller.

Insulation resistance: apply a megohmmeter, commonly at 500 volts DC, between each conductor and ground and between conductors; new signal wiring should read well above 10 megohms, and low readings indicate moisture or damaged insulation.

Continuity and fingerprinting: check every conductor end to end against the plan wiring diagram before terminations are made final, and record results for the acceptance package.

Ground test by three-point fall-of-potential, loop inductance and resistance measured at the cabinet, and a full conflict monitor and flash test before the intersection operates in stop-and-go.

Flash mode: new signals commonly run in flash for at least 24 hours, with advance public notice and notification to the agency and emergency services, before the switch to stop-and-go.

Turn-on procedure: keep heads covered or bagged and signs covered during construction, remove covers only at turn-on, then verify each phase, each pedestrian interval, and preemption from the field.

MUTCD Part 6 work zones: advance warning area, transition taper, buffer space, activity area, and termination area; a temporary signal must run continuously and be inspected for flash and power failure.

Flagger qualification: flaggers must be trained and, in most states, hold a current certification card from a recognized program; they need a clear escape route and must never be positioned in an open lane.

High-visibility apparel: ANSI/ISEA 107 Class 2 is the usual daylight minimum for roadway work, with Class 3 commonly required at night or where speeds and sight distance demand it.