IMSA Traffic Signal II key terms

A set of MUTCD conditions-such as traffic volume, crash history, pedestrians, or school crossings-used in an engineering study to decide whether a traffic signal is justified at a location.

The plan that assigns each intersection movement to a numbered phase and decides which movements get the right of way at the same time and in what order.

A left-turn operation that first displays a green arrow (protected) and later a circular green (permissive), so left turners must yield to opposing traffic during the permissive portion.

The yellow change plus all-red time after a green ends, sized so vehicles that cannot stop safely can clear the intersection before conflicting traffic is released.

The stretch of approach where a driver is too close to stop comfortably when yellow begins yet too far to clear before conflicting traffic moves.

A horizontal arm, usually tapered steel tube or truss, that projects from a signal pole to hold signal heads and signs out over the roadway.

An inductive wire loop saw-cut into the pavement that senses a vehicle by the change in inductance and sends a call to the controller.

Rigid or flexible pipe, such as PVC or galvanized steel, that carries signal cable underground or up a pole and shields it from water, soil, and physical damage.

A below-grade or at-grade box with a removable cover that gives access to conduit and cable so crews can pull, splice, or test conductors without excavating.

The concrete footing and embedded threaded bolts that anchor a signal pole or mast arm; alignment, elevation, and bolt projection must match the plans before concrete sets.

A tensioned cable strung between poles or structures that supports hanging signal heads; sag, tension, and attachment hardware determine head height and stability.

Bonding non-current-carrying metal parts-poles, cabinets, and controller frames-to earth through a grounding conductor and electrode so a fault trips the breaker instead of energizing metal.

The weather-resistant enclosure holding the controller, conflict monitor, detector units, and terminal blocks; its mounting, ventilation, and wiring must match the plans and standards.

The industry color sequence that identifies each conductor in a multi-conductor cable, letting crews match wires to the correct terminal at the pole and in the cabinet.

The total time, in seconds, for the controller to complete one full sequence of all phases and return to its starting point.

The share of the cycle length given to a phase, including its green, yellow, and all-red; splits for all phases add up to the cycle length.

The time difference between the start of the coordinated cycle at one intersection and the start at a neighboring intersection, used to time platoons through a corridor.

Operating several signals on a common cycle with planned offsets so vehicles traveling at the design speed meet mostly green lights.

Controller mode in which phases are called and extended by detectors instead of running a fixed sequence, so green is served only when traffic demands it.

When an actuated phase ends because no vehicle has extended the green within the passage time, meaning demand on that phase has dried up.

The longest time a phase may stay green while opposing demand is also waiting; reaching this limit forces the phase to terminate.

The shortest green time a phase will display once called, long enough to start vehicles queued between the stop bar and the detector.

Also called vehicle extension; the detector gap that must be exceeded before the controller ends green, allowing a following vehicle to keep the phase running.

The flashing DON'T WALK period after WALK, timed so a pedestrian who steps off the curb at the end of WALK can reach a refuge or the far curb.

A higher-priority command from an emergency vehicle, railroad, or transit system that overrides normal timing and runs a special sequence for the approaching vehicle or train.

A device that watches signal voltages for conflicting greens, faulty flash, or shorted outputs and, on detecting a fault, transfers the intersection to flashing operation.

The fail-safe condition in which a signal displays flashing red on some approaches and flashing yellow on others after a fault or on a set schedule.

An unintended path from an energized conductor to earth or metal parts, causing nuisance breaker trips or shock risk and often traced by insulation testing.

A test that applies high DC voltage to an isolated loop or cable and measures insulation resistance, showing whether moisture, damage, or a short is causing trouble.

Scheduled inspection, cleaning, tightening, and testing of signal equipment-lamps, lenses, detectors, cabinets, and hardware-performed before failures occur.

An uninterruptible power supply or battery system in the cabinet that keeps the controller and signal running for a limited time during a power outage.

Devices such as surge arrestors and metal-oxide varistors that shunt lightning and switching spikes to ground to protect the controller and detection circuits.

A procedure that de-energizes and locks a circuit before work so equipment cannot be restarted; the worker keeps the key and attaches a warning tag.

The Manual on Uniform Traffic Control Devices, the national standard adopted by FHWA and the states that governs design, placement, and operation of signs, signals, and markings.

A standard for traffic controller cabinets, controllers, and communications that defines connectors, voltage levels, and functions so equipment from different makers works together.

The portion of highway affected by construction or maintenance, organized into advance warning, transition, activity, and termination areas with signs, devices, and channelizing.

Controlling traffic through or around a work zone with a stop/slow paddle and hand signals, used when other devices cannot safely manage the movement.

A portable or trailer-mounted signal used to control alternating one-lane traffic or a temporary intersection during construction, with timing set for work zone conditions.

Garments meeting ANSI/ISEA 107 performance classes-vests, shirts, or jackets with retroreflective trim-required for workers and flaggers exposed to traffic.