1
IMSA Traffic Signal Technician 2 ACTUAL EXAM
QUESTIONS AND ANSWERS 2026/2027 | Study
Guide & Practice Test | NEMA TS1/TS2 | MUTCD
Compliance | Pass Guaranteed - A+ Graded
Part 1: Comprehensive Study Guide
A traffic signal cabinet requires 120 VAC but receives 132 VAC from the utility during off-peak
hours. Which transformer configuration is appropriate?
A. Buck configuration (10% reduction) [CORRECT]
B. Boost configuration (10% increase)
C. Isolation transformer 1:1 ratio
D. Step-down transformer 240V to 120V
Rationale: A buck-boost transformer in buck configuration reduces voltage by 10% (13.2V),
bringing 132V down to 118.8V—within the acceptable ±5% range (114-126V). Distractor B
would increase voltage to 145.2V, damaging equipment. Distractor C maintains 132V, which
exceeds equipment ratings. Distractor D is unnecessary and incorrect for this application.
Study Text: Grounding and Bonding (NEC Article 250)
Proper grounding protects against electric shock and equipment damage. Key requirements:
Grounding Electrode Conductor (GEC): Connects service equipment to earth
Equipment Grounding Conductor (EGC): Bonds non-current-carrying metal parts
Ground Bus: Common point for all cabinet ground connections
Isolated Ground: Separated ground path for sensitive electronics
NEC 250.4(A)(5) prohibits objectionable current on grounding conductors. This occurs when
neutral and ground are bonded at multiple points, creating parallel paths.
Tech Tip: Use a low-impedance ground tester (fall-of-potential method) to verify grounding
electrode resistance. NEC requires 25 ohms or less; IMSA recommends 5 ohms or less for signal
cabinets in lightning-prone areas.
Knowledge Check A2:
,2
During inspection, a technician finds the neutral and ground bars bonded together inside a traffic
signal cabinet AND at the service panel. What condition does this create?
A. Improved safety through redundant grounding
B. Objectionable current on grounding conductors [CORRECT]
C. Reduced voltage drop in the neutral conductor
D. Required configuration for TS2 cabinets
Rationale: Multiple neutral-to-ground bonds create parallel return paths for neutral current,
causing current to flow on grounding conductors. This violates NEC 250.6 and creates shock
hazards. Distractor A is dangerous—redundant grounding of the neutral is prohibited. Distractor
C is incorrect—voltage drop is not improved. Distractor D is false—TS2 standards do not
require this.
Study Text: Surge Protection & Load Calculations
Traffic signal systems require surge protection at multiple levels:
Service entrance: Type 1 SPD (permanently connected)
Branch panels: Type 2 SPD
Equipment level: Type 3 SPD (point-of-use)
Load calculations must account for continuous loads (signal heads) at 125% per NEC
210.19(A)(1). LED modules reduce load significantly compared to incandescent lamps.
Diagram Description [Figure A-1]: Typical traffic signal cabinet grounding layout showing GEC
connection to ground rod, ground bus bonding to cabinet frame, and isolated ground bus for
controller electronics with single-point connection to main ground bus.
Knowledge Check A3:
An intersection has 12 LED signal heads (12W each), a controller (150W), and detection
equipment (75W). What is the minimum branch circuit ampacity required per NEC?
A. 15 amps
B. 20 amps [CORRECT]
C. 25 amps
D. 30 amps
Rationale: Total load = (12 × 12W) + 150W + 75W = 144W + 225W = 369W. At 120V =
3.075A. Continuous load factor (1.25) = 3.84A. While 15A is technically sufficient, standard
,3
practice and future expansion capacity warrant 20A. Distractor A meets minimum but lacks
expansion capacity. Distractors C and D exceed requirements without justification.
Knowledge Check A4:
A Type 2 SPD installed in a traffic signal panel has indicator lights showing "Protection
Working" and "Line OK." After a lightning strike, the "Protection Working" light is off but
equipment operates normally. What does this indicate?
A. Normal operation—SPD always turns off after surge
B. SPD has sacrificed itself and requires replacement [CORRECT]
C. Ground connection has failed
D. Line voltage has dropped below threshold
Rationale: Metal oxide varistor (MOV)-based SPDs sacrifice themselves when absorbing surge
energy. The indicator shows protection is no longer active. Immediate replacement is required to
restore protection. Distractor A is incorrect—SPDs should remain active. Distractor C would
affect the "Line OK" indicator. Distractor D is unrelated to protection status.
Section B: TS1/TS2 Cabinet Components & Wiring
Study Text: NEMA TS1 vs. TS2 Architecture
NEMA standards define traffic signal control equipment interoperability:
TS1 (Traditional):
Discrete wiring between controller and load switches
120 VAC outputs from controller
Limited diagnostic capability
Simple conflict monitoring
TS2 (Modern):
Serial Data Link (SDLC) communication between controller and interface units
24 VDC logic levels with load switches providing 120 VAC output
Enhanced diagnostics and logging
Advanced malfunction management units (MMU)
Tech Tip: When troubleshooting TS2 cabinets, always check SDLC termination resistors
(typically 120Ω) at both ends of the serial bus. Missing terminators cause communication errors
and erratic signal operation.
, 4
Knowledge Check B1:
In a TS2 cabinet, the controller outputs 24 VDC logic signals to a device that switches 120 VAC
to signal heads. What is this device called?
A. Flash transfer relay
B. Load switch assembly [CORRECT]
C. Conflict monitor
D. Bus interface unit (BIU)
Rationale: TS2 load switches receive low-voltage logic from the controller and switch high-
voltage loads. They provide electrical isolation and current handling. Distractor A transfers
power during flash mode. Distractor C monitors conflicts but doesn't switch loads. Distractor D
handles SDLC communication, not load switching.
Study Text: Malfunction Management Unit (MMU)
The MMU monitors outputs for conflicts (green in multiple directions) and improper sequences.
Key features:
Red monitoring: Ensures all-red clearance before conflicting green
Voltmeter monitoring: Detects field wiring shorts/opens
Error logging: Records fault type and timestamp
Flash transfer: Forces intersection to flash on critical faults
Diagram Description [Figure B-1]: TS2 cabinet layout showing controller at top, MMU below,
load switch bays on right, and terminal blocks on left. SDLC cable routing shown in dashed lines
between controller, MMU, and BIUs.
Knowledge Check B2:
An MMU displays error code "E7 - Green Conflict." The intersection immediately transfers to
flash. What is the most likely cause?
A. Failed red LED in one signal head
B. Controller outputting green in conflicting directions simultaneously [CORRECT]
C. Loss of AC power to the cabinet
D. MMU programming error requiring recalibration
Rationale: E7 indicates the MMU detected voltage on green outputs for conflicting phases (e.g.,
northbound and eastbound simultaneously). This is a critical safety fault forcing flash mode.
IMSA Traffic Signal Technician 2 ACTUAL EXAM
QUESTIONS AND ANSWERS 2026/2027 | Study
Guide & Practice Test | NEMA TS1/TS2 | MUTCD
Compliance | Pass Guaranteed - A+ Graded
Part 1: Comprehensive Study Guide
A traffic signal cabinet requires 120 VAC but receives 132 VAC from the utility during off-peak
hours. Which transformer configuration is appropriate?
A. Buck configuration (10% reduction) [CORRECT]
B. Boost configuration (10% increase)
C. Isolation transformer 1:1 ratio
D. Step-down transformer 240V to 120V
Rationale: A buck-boost transformer in buck configuration reduces voltage by 10% (13.2V),
bringing 132V down to 118.8V—within the acceptable ±5% range (114-126V). Distractor B
would increase voltage to 145.2V, damaging equipment. Distractor C maintains 132V, which
exceeds equipment ratings. Distractor D is unnecessary and incorrect for this application.
Study Text: Grounding and Bonding (NEC Article 250)
Proper grounding protects against electric shock and equipment damage. Key requirements:
Grounding Electrode Conductor (GEC): Connects service equipment to earth
Equipment Grounding Conductor (EGC): Bonds non-current-carrying metal parts
Ground Bus: Common point for all cabinet ground connections
Isolated Ground: Separated ground path for sensitive electronics
NEC 250.4(A)(5) prohibits objectionable current on grounding conductors. This occurs when
neutral and ground are bonded at multiple points, creating parallel paths.
Tech Tip: Use a low-impedance ground tester (fall-of-potential method) to verify grounding
electrode resistance. NEC requires 25 ohms or less; IMSA recommends 5 ohms or less for signal
cabinets in lightning-prone areas.
Knowledge Check A2:
,2
During inspection, a technician finds the neutral and ground bars bonded together inside a traffic
signal cabinet AND at the service panel. What condition does this create?
A. Improved safety through redundant grounding
B. Objectionable current on grounding conductors [CORRECT]
C. Reduced voltage drop in the neutral conductor
D. Required configuration for TS2 cabinets
Rationale: Multiple neutral-to-ground bonds create parallel return paths for neutral current,
causing current to flow on grounding conductors. This violates NEC 250.6 and creates shock
hazards. Distractor A is dangerous—redundant grounding of the neutral is prohibited. Distractor
C is incorrect—voltage drop is not improved. Distractor D is false—TS2 standards do not
require this.
Study Text: Surge Protection & Load Calculations
Traffic signal systems require surge protection at multiple levels:
Service entrance: Type 1 SPD (permanently connected)
Branch panels: Type 2 SPD
Equipment level: Type 3 SPD (point-of-use)
Load calculations must account for continuous loads (signal heads) at 125% per NEC
210.19(A)(1). LED modules reduce load significantly compared to incandescent lamps.
Diagram Description [Figure A-1]: Typical traffic signal cabinet grounding layout showing GEC
connection to ground rod, ground bus bonding to cabinet frame, and isolated ground bus for
controller electronics with single-point connection to main ground bus.
Knowledge Check A3:
An intersection has 12 LED signal heads (12W each), a controller (150W), and detection
equipment (75W). What is the minimum branch circuit ampacity required per NEC?
A. 15 amps
B. 20 amps [CORRECT]
C. 25 amps
D. 30 amps
Rationale: Total load = (12 × 12W) + 150W + 75W = 144W + 225W = 369W. At 120V =
3.075A. Continuous load factor (1.25) = 3.84A. While 15A is technically sufficient, standard
,3
practice and future expansion capacity warrant 20A. Distractor A meets minimum but lacks
expansion capacity. Distractors C and D exceed requirements without justification.
Knowledge Check A4:
A Type 2 SPD installed in a traffic signal panel has indicator lights showing "Protection
Working" and "Line OK." After a lightning strike, the "Protection Working" light is off but
equipment operates normally. What does this indicate?
A. Normal operation—SPD always turns off after surge
B. SPD has sacrificed itself and requires replacement [CORRECT]
C. Ground connection has failed
D. Line voltage has dropped below threshold
Rationale: Metal oxide varistor (MOV)-based SPDs sacrifice themselves when absorbing surge
energy. The indicator shows protection is no longer active. Immediate replacement is required to
restore protection. Distractor A is incorrect—SPDs should remain active. Distractor C would
affect the "Line OK" indicator. Distractor D is unrelated to protection status.
Section B: TS1/TS2 Cabinet Components & Wiring
Study Text: NEMA TS1 vs. TS2 Architecture
NEMA standards define traffic signal control equipment interoperability:
TS1 (Traditional):
Discrete wiring between controller and load switches
120 VAC outputs from controller
Limited diagnostic capability
Simple conflict monitoring
TS2 (Modern):
Serial Data Link (SDLC) communication between controller and interface units
24 VDC logic levels with load switches providing 120 VAC output
Enhanced diagnostics and logging
Advanced malfunction management units (MMU)
Tech Tip: When troubleshooting TS2 cabinets, always check SDLC termination resistors
(typically 120Ω) at both ends of the serial bus. Missing terminators cause communication errors
and erratic signal operation.
, 4
Knowledge Check B1:
In a TS2 cabinet, the controller outputs 24 VDC logic signals to a device that switches 120 VAC
to signal heads. What is this device called?
A. Flash transfer relay
B. Load switch assembly [CORRECT]
C. Conflict monitor
D. Bus interface unit (BIU)
Rationale: TS2 load switches receive low-voltage logic from the controller and switch high-
voltage loads. They provide electrical isolation and current handling. Distractor A transfers
power during flash mode. Distractor C monitors conflicts but doesn't switch loads. Distractor D
handles SDLC communication, not load switching.
Study Text: Malfunction Management Unit (MMU)
The MMU monitors outputs for conflicts (green in multiple directions) and improper sequences.
Key features:
Red monitoring: Ensures all-red clearance before conflicting green
Voltmeter monitoring: Detects field wiring shorts/opens
Error logging: Records fault type and timestamp
Flash transfer: Forces intersection to flash on critical faults
Diagram Description [Figure B-1]: TS2 cabinet layout showing controller at top, MMU below,
load switch bays on right, and terminal blocks on left. SDLC cable routing shown in dashed lines
between controller, MMU, and BIUs.
Knowledge Check B2:
An MMU displays error code "E7 - Green Conflict." The intersection immediately transfers to
flash. What is the most likely cause?
A. Failed red LED in one signal head
B. Controller outputting green in conflicting directions simultaneously [CORRECT]
C. Loss of AC power to the cabinet
D. MMU programming error requiring recalibration
Rationale: E7 indicates the MMU detected voltage on green outputs for conflicting phases (e.g.,
northbound and eastbound simultaneously). This is a critical safety fault forcing flash mode.
