Free IMSA TST-I Exam Flashcards

The major-street through movements. Even-numbered phases are always through movements, and 2/6 typically get the longest green in the cycle.

A group of phases that time sequentially (one at a time) within a controller. Two rings can run concurrently as long as they cross a barrier together.

A barrier — the point in the cycle where both rings must finish their current phases before advancing, so only compatible movements are ever paired.

A gap out — the phase terminates efficiently because there is no call to extend the green, as opposed to being cut off at the max green limit.

A max out — the controller forces the phase to end because a conflicting phase has been waiting since before max green was reached.

The all-red (red clearance) interval — it gives vehicles that entered the intersection during yellow time to clear before opposing traffic gets a green.

3.5 feet per second. A slower default (e.g., 3.0 ft/sec) may be used at locations with higher concentrations of slower pedestrians.

Yes, but only after yielding to oncoming traffic and pedestrians. A green ball is a permissive indication, unlike a green arrow, which grants protected (exclusive) right-of-way.

A permissive left turn — drivers may turn after yielding to oncoming traffic and pedestrians, giving more flexible left-turn phasing than a simple green ball.

Preemption (e.g., for a train) immediately interrupts and overrides normal signal timing and takes the highest priority; priority only adjusts timing (extends/shortens phases) without overriding it.

The load switch — it receives low-voltage logic signals from the controller and switches full line voltage to the actual signal lamp/LED circuit.

It forces the intersection into flash mode (typically flashing red on all approaches) as a fail-safe, since it can only detect and shut down the conflict, not correct it.

TS1 uses a basic conflict monitor with hardwired inputs; TS2 uses a Malfunction Management Unit (MMU) that communicates over a serial data bus (SDLC), enabling broader fault detection.

4 amps (I = V / R = 12 / 3 = 4A). Ohm's Law (V = I x R) is the foundational relationship a technician uses to diagnose circuit behavior.

Total parallel resistance is always LESS than the smallest individual resistor — the opposite of series circuits, where resistances simply add together.

It tests insulation resistance by applying a high test voltage; a low reading indicates damaged or wet insulation that could let current leak to ground or a nearby conductor.

The 80% continuous-load rule requires the breaker be sized so the continuous load never exceeds 80% of its rating, preventing nuisance trips and heat buildup from prolonged full-load operation.

A call is a one-time request for service (e.g., from a detector); a recall is a standing instruction that keeps placing a phase in demand every cycle regardless of detector input.

Semi-actuated has detectors only on the minor/side-street approaches (the main street rests in green); fully-actuated has detectors on all approaches, so every phase's timing depends on demand.

A GFI/GFCI (ground fault circuit interrupter) — it protects technicians from shock by cutting power well before a lethal current level is reached.

A 6x6-foot quadrupole loop. The quadrupole (figure-eight) winding pattern improves detection sensitivity and reduces interference from adjacent lanes.

Pavement cracking or shifting that breaks the loop wire — pavement movement over time is the leading cause of intermittent or total loop failure.

Loop lead-in uses IMSA Spec 50-2 (shielded twisted pair); signal and interconnect cable uses IMSA Spec 19-1 or 20-1 — mixing these up is a common exam trap.

It analyzes camera pixel changes above the pavement rather than embedding a wire in the roadway, but this makes it more sensitive to weather, glare, and lighting conditions.

Vehicle speed and directional presence — radar/microwave detectors reflect a signal off the vehicle to calculate speed in addition to simple presence detection.

It places a pedestrian call (demand) for that phase. The walk interval is not served instantly — it is served according to the controller's timing and current phase sequence.

The detector amplifier (loop amplifier card), typically mounted in a detector rack in the cabinet — it senses the inductance change and outputs a call.

First check and adjust detector sensitivity; if that doesn't resolve it, perform a megger test on the loop wire to check for a broken conductor or damaged insulation.

A mast arm is a rigid, cantilevered pole-mounted structure; a span wire is a cable strung between strain poles that suspends the signal heads. Mast arms are more rigid and need less maintenance.

A pull box (handhole) — it lets technicians pull, splice, or troubleshoot cable without excavating the conduit run.

It prevents water from running down the cable and into the equipment enclosure — the loop lets water drip off at the low point instead of tracking inside.

Roughly 40% of the conduit's cross-sectional area. Exceeding this makes pulling cable difficult and can cause overheating or block future cable additions.

Power at the cabinet — a total dark signal points to a power supply or main breaker failure, so power is checked before controller logic or field wiring.

Power first, then controller/logic, then load switches, then field wiring/heads — working from the source of power outward isolates the fault fastest.

Secure the scene and establish traffic control before doing any repair work — safety of the traveling public and crew comes before restoring the signal.

A Standard is a mandatory requirement (uses 'shall'); Guidance is a recommended practice (uses 'should') that may be deviated from with engineering judgment.

Option describes a permissive practice ('may') that is allowed but not required; Support is purely informational background text with no compliance obligation.

Nine warrants. Meeting one or more warrants justifies further engineering study but does not by itself mandate signal installation.

The 11th Edition, effective January 18, 2024 — it is the current version referenced for signal indications, warrants, and device standards.

NEC Article 250 — it specifies grounding electrode, bonding, and ground rod resistance requirements to protect equipment and personnel from fault current.

Green, or green with a yellow stripe. This color coding distinguishes the equipment grounding conductor from ungrounded (hot) and grounded neutral conductors, and is a frequently tested wiring-ID detail.

25 ohms or less. If one rod tests above this, a second ground rod must be added and bonded to bring the combined resistance within limits.

It supports much higher bandwidth over longer distances with far less signal loss or electrical interference than copper twisted-pair cable.

When trenching new conduit or cable is not feasible due to cost, right-of-way, or terrain — wireless avoids needing a physical cable run entirely.

An OTDR (Optical Time-Domain Reflectometer) — it sends a light pulse down the fiber and measures reflections to pinpoint breaks or splice loss.

It coordinates timing among multiple local intersection controllers so they operate on a common offset/cycle, without needing a full central traffic management system.

Baud rate (and device address) mismatch — serial communication requires both ends configured to the same data rate and addressing scheme.

LOTO (Lockout/Tagout) — power sources are locked and tagged out so the equipment cannot be unexpectedly energized while a technician is working on it.

Class C — it uses a non-conductive extinguishing agent that is safe to use on live electrical equipment, unlike water-based extinguishers.

Do not touch it. Secure the area, keep the public away, and contact the utility company to de-energize the line before any signal repair work begins.