IMSA Traffic Signal III flashcards
IMSA Traffic Signal III · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Yellow change interval formula
- Y = t + v / (2a + 2gG). It combines perception-reaction time with braking distance converted to time, accounting for approach speed, deceleration, and grade.
- Red clearance interval
- The time after yellow when all approaches display red, calculated as (W + L) / v so a vehicle can clear the intersection before conflicting traffic is released.
- NEMA phase numbering
- Standard phase numbers assign vehicle movements to controller phases, typically 1 through 8 for a basic eight-phase intersection, with overlaps for shared movements.
- Pedestrian walk interval
- The WALK indication should be at least 7 seconds and long enough for pedestrians to leave the curb before flashing DON'T WALK begins.
- Flashing DON'T WALK timing
- Pedestrian clearance time equals crossing distance divided by walking speed, commonly 3.5 feet per second, plus a buffer where required by agency policy.
- Dilemma zone
- The approach area where a driver may be unable to stop comfortably or clear the intersection before red; detection or timing adjustments can reduce exposure.
- Conflict matrix check
- A plan-review check that lists compatible and incompatible movements to confirm no phase or overlap can display conflicting green indications simultaneously.
- Anchor bolt template
- A fixture that holds foundation anchor bolts in the correct pattern and orientation; verify it before and after concrete placement so poles fit.
- Conduit bend limit
- Total bends between pull points should not exceed 360 degrees; more bends make cable pulling difficult and can damage conductors or insulation.
- Inductive loop saw cut
- The saw-cut slot that receives loop wire; it must be clean and dry, sealed against moisture, and tested for inductance and resistance before connection.
- Span wire clearance
- The vertical distance from the roadway to signal heads and span hardware; verify against agency standards and electrical code before energizing.
- Cabinet grounding
- Bonding the controller cabinet, poles, and metallic equipment to the grounding electrode system; confirm continuity and proper separation of power and signal circuits.
- Point-to-point wiring test
- A continuity and identification check from cabinet terminals to field devices that verifies conductor assignments before power is applied.
- NEMA TS 2
- A controller and cabinet standard defining Type 1 and Type 2 architectures, detector racks, load switches, and serial communication for traffic signal systems.
- ATC controller
- Advanced Transportation Controller, an open-architecture controller standard using modern processors and standardized interfaces for traffic and field-device control.
- Gap-out
- An actuated phase ends when no detector call remains during the passage time, allowing the controller to serve another phase.
- Max-out
- A phase terminates at its maximum green setting even if a detector call remains, protecting the coordinated cycle and preventing excessive delay.
- Conflict monitor
- A malfunction management unit that monitors field signal voltages and places the intersection in flash when it detects conflicting greens or other unsafe faults.
- NTCIP
- National Transportation Communications for ITS Protocol, a family of standardized object definitions and communication rules used for traffic controllers and field devices.
- Presence detection
- A detection mode that maintains a continuous call while a vehicle occupies the detection zone, commonly used at stop bars for actuated control.
- MMU flash mode
- The conflict monitor's safe state, flashing red or yellow as configured, entered when a monitored fault such as a conflicting green is detected.
- Preventive maintenance
- Scheduled inspection and servicing of cabinets, signal heads, detection, communications, and support structures to find faults before they cause failures.
- Load switch
- A cabinet device that switches field signal lamp or LED circuits on and off in response to controller outputs; a failed switch can cause a color outage.
- Detector loop tester
- A field instrument that measures loop inductance and can indicate opens, shorts, or excessive resistance in loop wire and lead-in circuits.
- Timing plan update
- A revision of cycle length, splits, offsets, and pedestrian timings based on field data; verify operation after loading the new database.
- Preemption check
- Testing that emergency or railroad preemption detectors, receivers, and controller timing properly interrupt normal operation and restore it safely.
- MUTCD Part 4
- The federal standard for highway traffic signals, covering warrants, signal displays, phasing, pedestrian control, and traffic signal design and operation.
- MUTCD Part 6
- The federal standard for temporary traffic control, covering work-zone signs, channelizing devices, tapers, flaggers, and temporary signals.
- Flashing red indication
- A signal display requiring drivers to stop and then proceed when safe, often used during signal malfunction or at specific intersections.
- Temporary traffic signal
- A portable or work-zone signal used to control alternating traffic; it must be coordinated with signing, flaggers, and channelizing devices.
- Lockout/tagout
- A safety procedure that isolates and secures energy sources before servicing electrical equipment to prevent unexpected energization or release of stored energy.
- ADA push button
- An accessible pedestrian push button requires a level landing, clear floor space, reachable mounting height, and orientation toward the crossing it controls.