IMSA Signal Construction key terms

A scaled drawing in the contract plans showing the location, dimensions, and details of signal work-poles, conduit runs, cabinets, and signal heads-that the contractor uses to lay out and build the installation.

The contract book of general requirements covering materials, construction methods, and measurement and payment for each item of work, applied unless the plans or special provisions state otherwise.

Project-specific written requirements that modify, add to, or delete portions of the standard specifications for a particular contract; they govern wherever they conflict with the general specifications.

A detailed drawing submitted by the contractor showing how equipment or structures will be fabricated and assembled-dimensions, materials, bolts, and connections-so the engineer can verify compliance with the contract before construction.

Distance measured along a baseline or roadway centerline and written in stations, usually 100-foot units, used to locate poles, cabinets, conduit, and other plan features on the ground.

The curved edge connecting two intersecting curbs or pavement edges; it controls turning paths, the length and placement of crosswalks, and where pedestrian push buttons and poles may be installed.

The unobstructed roadside area measured from the edge of the traveled way that should stay free of fixed objects; poles, cabinets, and foundations must sit outside it or be protected by an approved barrier.

The length of roadway a driver must be able to see to stop or react safely; signal heads, poles, signs, and vegetation are placed and maintained so this view is not blocked.

A fixed point of known elevation, such as a marked disk or hub, from which all vertical measurements on the project are referenced; it must be protected and rechecked before foundations are set.

A stake set a measured distance away from the actual construction point and marked with the offset and cut or fill, allowing the point to be re-established after excavation destroys the original mark.

A rigid jig, often plywood or steel, that holds anchor bolts at the correct spacing, bolt-circle diameter, and projection while foundation concrete is placed so the pole or cabinet base will fit.

A drilled or excavated concrete column, typically reinforced and fitted with anchor bolts, that supports a signal pole or mast arm and resists overturning, uplift, and torsion from wind and wire loads.

A layer of sand, select granular material, or controlled low-strength material placed in the trench bottom to support conduit evenly and protect it from rock, debris, and point loading before backfill.

An accessible buried or flush enclosure in a conduit run where cables can be pulled, spliced, or redirected; required where runs are long or contain enough bends to exceed pulling limits.

A durable, usually insulated conductor laid alongside nonmetallic conduit or direct-buried cable so the buried route can be located later with a locating instrument, reducing damage during future excavation.

The least depth of soil, base, or pavement required above the top of a conduit or duct, set by the specifications to protect it from traffic loads and routine excavation.

A horizontal or slightly arched structural arm attached to a pole that carries signal heads and signs out over the roadway, designed for wind, ice, and dead loads.

A tensioned wire suspended between two poles or structures from which signal heads and signs hang; the poles, guys, and anchors must be sized for the combined wire and equipment loads.

A pole sized and founded specifically to resist the one-directional pull of span wires or guys, usually with a heavier foundation or an anchor installed opposite the wire load.

A buried device-screw anchor, plate, or concrete deadman-connected to a pole by a guy wire to resist lateral or unbalanced loads and keep the pole plumb.

The standard, project-specified assignment of colors or tracers to conductors in a cable so each circuit can be identified and terminated at the same point at both ends.

A plan table listing each cable by tag number, size, conductor count, routing from and to, and length, used to pull, label, and terminate conductors correctly.

A cable run from a field device straight back to the controller cabinet with no intermediate splices or junction points, which simplifies testing and troubleshooting.

The minimum radius to which a cable or conduit may be bent without damaging conductors or insulation; conduit bends must also be large enough to keep cable pulling within its own limit.

One complete set of signal indications-typically red, yellow, and green-aimed at a single approach or lane group; a signal head may contain one or more faces.

A contrasting, usually black, panel mounted behind a signal face to make the indications stand out against bright or cluttered backgrounds such as sky, signs, or buildings.

A hood projecting from the front of a signal lens that shields it from sunlight, reducing phantom indications and improving contrast; cutaway visors are used where drivers stop close to the head.

A false signal appearance, most often caused by sunlight reflecting off a lens or by a signal face aimed toward traffic it does not control; visors, backplates, and proper aiming reduce it.

A pedestrian signal that supplements the visual display with audible and tactile information-locator tones, speech messages, and a vibrating arrow-so pedestrians with vision impairments can cross safely.

The weatherproof enclosure, usually aluminum or stainless steel, that houses the signal controller, power distribution, detector units, conflict monitoring, and terminal facilities for the intersection.

A monitoring device that watches signal outputs for conflicts, shorts, or field failures and, when a fault is detected, forces the intersection into flashing operation until the problem is corrected.

A loop of wire embedded in the pavement and connected to an amplifier in the cabinet; passing vehicles change the loop's inductance and generate a call for the controller.

The cabinet card that energizes a loop or other sensor, tunes it to a stable operating point, and converts detected vehicle presence into calls the controller can process.

A copper-clad or galvanized rod driven into the earth and bonded to cabinet, pole, and equipment grounds to provide a low-resistance path for fault current and surge energy.

A test in which a megohmmeter applies high direct voltage between conductors and from conductors to ground to confirm insulation is intact and dry before equipment is connected.

Operating every signal indication, pedestrian display, detector, and auxiliary device from the controller to verify the installed system performs as designed before the intersection is placed in service.

The coordinated procedure for placing a new or rebuilt signal in service, usually beginning in flashing mode and followed by stop-and-go operation with the engineer and agency present.

A drawing and written description of how traffic, pedestrians, and workers will be protected through a work zone, including signs, channelizing devices, tapers, and flagging.