IMSA Signal Inspector cheat sheet

Inspection sequence: verify approved plans and permits, then cabinet/controller, then power and grounding, then detection, then display and wiring, then timing and conflict monitor, then final operational test with the signal in recall/stop-time.

Conflict monitor (MMU) test: place the monitor in program card test mode, verify all red, yellow, and green field outputs are sensed correctly, confirm fault latch on simulated conflicting greens, and record the monitor's response time against the specification.

Loop detection verification: use an ohmmeter or loop tester to confirm inductance and resistance within the manufacturer's range, check feeder twist (minimum 3 to 4 twists per foot for the home-run pair), and confirm the detector card detects a vehicle at the stop bar and at the advance zone.

Video and radar detection verification: confirm detection zones on the plan view, verify presence and pulse modes, check zone boundaries against stop-bar and setback dimensions, and record any occlusion from signs, poles, or foliage.

Pedestrian signal verification: confirm accessible pedestrian signal (APS) audible and vibrotactile output, pushbutton activation, clearance intervals, and that the walk symbol and countdown display match the programmed timing.

Visual display check: verify each lens and backplate is clean, aligned, and free of water intrusion; confirm visor condition, lamp or LED module color, and that the signal head faces approaching traffic per the plan.

Grounding verification: confirm the service ground, cabinet ground rod (typically 8 ft or per specification), and equipment bonding are continuous; measure ground resistance with a fall-of-potential or clamp-on tester and record the value.

Timing verification: compare the controller's programmed intervals (green, yellow, all-red, pedestrian walk and clearance) to the approved timing chart, and confirm coordination offsets and cycle length against the plan.

Documentation: record all measured values, serial numbers, firmware versions, and any deficiencies on the inspection form; a signal is not accepted until punch-list items are corrected and re-verified.

Cabinet types: NEMA TS 1 and TS 2 use a Type 1 or Type 2 cabinet with a 170/2070-style controller; ATC cabinets (per ATC 5201/5301) use an ATC controller with an SDLC or Ethernet backplane and are typically NEMA TS 2 or ATC-compliant.

Controller modes: pre-timed (fixed time), actuated (vehicle/pedestrian actuation), semi-actuated (mainline free, side street actuated), and adaptive (real-time plan selection based on detector data).

MMU vs. CMU: the malfunction management unit monitors conflict, red failure, and other fault conditions in NEMA TS 2 cabinets; the conflict monitor unit serves the same role in 170/2070 cabinets; both drive the signal to flash on a fault.

Cabinet power: verify 120 VAC service, circuit breakers, surge protection, and the uninterruptible power supply or battery backup; confirm the load switch and flash transfer relay operate correctly.

Controller firmware and configuration: record the firmware version, database file, and configuration settings; confirm the controller is loaded with the approved timing plan and that the database is backed up.

SDLC and communications: verify the serial data link between the controller and the MMU, detector racks, and auxiliary devices; confirm the Ethernet or serial link to the central system is active and the controller is online.

Flash operation: on loss of power or a fault, the cabinet must transfer to flashing yellow on the mainline and flashing red on the side street (or per the approved flash plan); verify the flash transfer relay and the flash rate (typically 50 to 60 flashes per minute).

Cabinet environmental controls: confirm the fan, filter, heater, and thermostat operate; check for water intrusion, corrosion, and pest entry; verify the door seal and the cabinet is locked and secured.

Wiring and terminal checks: verify terminal block torque, wire labels, and that spare conductors are capped; confirm the cabinet wiring matches the approved wiring diagram and that no unauthorized modifications exist.

Signal head configuration: a standard 3-section head has red, yellow, and green lenses; a 4-section head adds a protected left-turn arrow; a 5-section head adds a protected right-turn arrow or a second left-turn arrow, depending on the design.

Lens and backplate standards: lenses must be the correct color and size (typically 12-inch for through movements, 8-inch in some applications), backplates must be present and non-reflective, and visors must be cut off or full-circle per the plan.

Signal display mounting: signal heads must be mounted at the correct height (typically 15 to 19 ft above the roadway for span-wire and mast-arm installations) and aligned to face approaching traffic.

Detection types: inductive loop, video, radar, magnetometer, and pushbutton; each has specific installation requirements for spacing, setback, and orientation relative to the stop bar.

Inductive loop installation: loops are typically saw-cut into the pavement, sealed with loop sealant, and connected to the cabinet via twisted pair; loop size and turns determine inductance, and the feeder wire must be twisted to reduce noise.

Wiring color code (NEMA): red for red display, yellow for yellow display, green for green display, white for neutral, black for hot, and green or bare for ground; confirm the field wiring matches the cabinet terminal assignments.

Conductor sizing: signal display circuits are typically 14 AWG; detector loops use 14 or 16 AWG; power circuits use 12 AWG or larger per the load calculation and the National Electrical Code.

Pedestrian pushbutton wiring: confirm the pushbutton is wired to the correct input, the accessible pedestrian signal (APS) is programmed for the correct message, and the pushbutton is mounted at an accessible height (typically 42 inches above grade).

Splice and connection standards: all splices must be in approved enclosures, use waterproof connectors, and be accessible for inspection; direct-buried splices are not permitted.

Temporary traffic control (TTC) plan: a work zone affecting a signalized intersection must have an approved TTC plan per the Manual on Uniform Traffic Control Devices (MUTCD) Part 6, including advance warning, taper, buffer, and termination areas.

Flagger and worker safety: flaggers must be trained and certified, wear high-visibility apparel (Class 2 or 3 per the MUTCD), and use stop/slow paddles; workers must be protected by positive protection or a buffer space.

Signal work in a work zone: when a signal is taken out of service, the intersection must be controlled by flaggers or temporary signals; the contractor must notify the agency and emergency services before deactivation.

Coordination with construction: the inspector must verify the contractor's schedule, submittals, and traffic control plan; any change to the signal timing or configuration must be approved by the agency before implementation.

Recordkeeping: maintain daily inspection reports, as-built drawings, test results, material certifications, and punch lists; all records must be retained per the agency's retention schedule.

As-built documentation: record the final location of all conduits, loops, poles, and cabinets; update the signal timing chart and the cabinet wiring diagram to reflect field conditions.

Substantial completion and acceptance: the signal is accepted after all tests pass, punch-list items are corrected, and the agency issues a written acceptance; warranty periods typically begin at acceptance.

Traffic signal permits: confirm the contractor has the required permits (right-of-way, electrical, and signal) before work begins; verify the permit conditions are met throughout construction.

Incident and deficiency reporting: any safety hazard, damage to existing utilities, or nonconforming work must be documented and reported to the agency immediately; corrective action must be tracked to closure.

Inspection sequence: verify approved plans and permits, then cabinet/controller, then power and grounding, then detection, then display and wiring, then timing and conflict monitor, then final operational test with the signal in recall/stop-time.

Conflict monitor (MMU) test: place the monitor in program card test mode, verify all red, yellow, and green field outputs are sensed correctly, confirm fault latch on simulated conflicting greens, and record the monitor's response time against the specification.

Loop detection verification: use an ohmmeter or loop tester to confirm inductance and resistance within the manufacturer's range, check feeder twist (minimum 3 to 4 twists per foot for the home-run pair), and confirm the detector card detects a vehicle at the stop bar and at the advance zone.

Video and radar detection verification: confirm detection zones on the plan view, verify presence and pulse modes, check zone boundaries against stop-bar and setback dimensions, and record any occlusion from signs, poles, or foliage.

Pedestrian signal verification: confirm accessible pedestrian signal (APS) audible and vibrotactile output, pushbutton activation, clearance intervals, and that the walk symbol and countdown display match the programmed timing.

Visual display check: verify each lens and backplate is clean, aligned, and free of water intrusion; confirm visor condition, lamp or LED module color, and that the signal head faces approaching traffic per the plan.

Grounding verification: confirm the service ground, cabinet ground rod (typically 8 ft or per specification), and equipment bonding are continuous; measure ground resistance with a fall-of-potential or clamp-on tester and record the value.

Timing verification: compare the controller's programmed intervals (green, yellow, all-red, pedestrian walk and clearance) to the approved timing chart, and confirm coordination offsets and cycle length against the plan.

Documentation: record all measured values, serial numbers, firmware versions, and any deficiencies on the inspection form; a signal is not accepted until punch-list items are corrected and re-verified.

Cabinet types: NEMA TS 1 and TS 2 use a Type 1 or Type 2 cabinet with a 170/2070-style controller; ATC cabinets (per ATC 5201/5301) use an ATC controller with an SDLC or Ethernet backplane and are typically NEMA TS 2 or ATC-compliant.

Controller modes: pre-timed (fixed time), actuated (vehicle/pedestrian actuation), semi-actuated (mainline free, side street actuated), and adaptive (real-time plan selection based on detector data).

MMU vs. CMU: the malfunction management unit monitors conflict, red failure, and other fault conditions in NEMA TS 2 cabinets; the conflict monitor unit serves the same role in 170/2070 cabinets; both drive the signal to flash on a fault.

Cabinet power: verify 120 VAC service, circuit breakers, surge protection, and the uninterruptible power supply or battery backup; confirm the load switch and flash transfer relay operate correctly.

Controller firmware and configuration: record the firmware version, database file, and configuration settings; confirm the controller is loaded with the approved timing plan and that the database is backed up.

SDLC and communications: verify the serial data link between the controller and the MMU, detector racks, and auxiliary devices; confirm the Ethernet or serial link to the central system is active and the controller is online.

Flash operation: on loss of power or a fault, the cabinet must transfer to flashing yellow on the mainline and flashing red on the side street (or per the approved flash plan); verify the flash transfer relay and the flash rate (typically 50 to 60 flashes per minute).

Cabinet environmental controls: confirm the fan, filter, heater, and thermostat operate; check for water intrusion, corrosion, and pest entry; verify the door seal and the cabinet is locked and secured.

Wiring and terminal checks: verify terminal block torque, wire labels, and that spare conductors are capped; confirm the cabinet wiring matches the approved wiring diagram and that no unauthorized modifications exist.

Signal head configuration: a standard 3-section head has red, yellow, and green lenses; a 4-section head adds a protected left-turn arrow; a 5-section head adds a protected right-turn arrow or a second left-turn arrow, depending on the design.

Lens and backplate standards: lenses must be the correct color and size (typically 12-inch for through movements, 8-inch in some applications), backplates must be present and non-reflective, and visors must be cut off or full-circle per the plan.

Signal display mounting: signal heads must be mounted at the correct height (typically 15 to 19 ft above the roadway for span-wire and mast-arm installations) and aligned to face approaching traffic.

Detection types: inductive loop, video, radar, magnetometer, and pushbutton; each has specific installation requirements for spacing, setback, and orientation relative to the stop bar.

Inductive loop installation: loops are typically saw-cut into the pavement, sealed with loop sealant, and connected to the cabinet via twisted pair; loop size and turns determine inductance, and the feeder wire must be twisted to reduce noise.

Wiring color code (NEMA): red for red display, yellow for yellow display, green for green display, white for neutral, black for hot, and green or bare for ground; confirm the field wiring matches the cabinet terminal assignments.

Conductor sizing: signal display circuits are typically 14 AWG; detector loops use 14 or 16 AWG; power circuits use 12 AWG or larger per the load calculation and the National Electrical Code.

Pedestrian pushbutton wiring: confirm the pushbutton is wired to the correct input, the accessible pedestrian signal (APS) is programmed for the correct message, and the pushbutton is mounted at an accessible height (typically 42 inches above grade).

Splice and connection standards: all splices must be in approved enclosures, use waterproof connectors, and be accessible for inspection; direct-buried splices are not permitted.

Temporary traffic control (TTC) plan: a work zone affecting a signalized intersection must have an approved TTC plan per the Manual on Uniform Traffic Control Devices (MUTCD) Part 6, including advance warning, taper, buffer, and termination areas.

Flagger and worker safety: flaggers must be trained and certified, wear high-visibility apparel (Class 2 or 3 per the MUTCD), and use stop/slow paddles; workers must be protected by positive protection or a buffer space.

Signal work in a work zone: when a signal is taken out of service, the intersection must be controlled by flaggers or temporary signals; the contractor must notify the agency and emergency services before deactivation.

Coordination with construction: the inspector must verify the contractor's schedule, submittals, and traffic control plan; any change to the signal timing or configuration must be approved by the agency before implementation.

Recordkeeping: maintain daily inspection reports, as-built drawings, test results, material certifications, and punch lists; all records must be retained per the agency's retention schedule.

As-built documentation: record the final location of all conduits, loops, poles, and cabinets; update the signal timing chart and the cabinet wiring diagram to reflect field conditions.

Substantial completion and acceptance: the signal is accepted after all tests pass, punch-list items are corrected, and the agency issues a written acceptance; warranty periods typically begin at acceptance.

Traffic signal permits: confirm the contractor has the required permits (right-of-way, electrical, and signal) before work begins; verify the permit conditions are met throughout construction.

Incident and deficiency reporting: any safety hazard, damage to existing utilities, or nonconforming work must be documented and reported to the agency immediately; corrective action must be tracked to closure.