IMSA TRAFFIC SIGNAL CORE MAIN QUESTIONS
AND ANSWERS SURE A+
✔✔Ped heads mounting -✔✔Between 7 to 10 ft from bottom of head to sidewalk level
✔✔Ground fault circuit interruptor (GFCI) -✔✔Protect devices and workers from eletrical
shock. Trip with overload in 1/40th of second. Never plug cabinet equipment into GFCI
✔✔Mercury Contractor -✔✔Supply AC power to load switches. Being replaced with
SSRs (solid state) or hybrid relays
✔✔Signal phase locations -✔✔min 40', max 180'. If longer than 180' need supplemental
signal head
✔✔Fan/thermostat -✔✔Heat dissipation temp regulation 85-165 (170) moisture control
✔✔Communication components -✔✔Allow cabinet to connect with centralized
management system or other devices
✔✔UPS -✔✔Uninterruptable power supply aka battery backup
✔✔Maintenance switch panel -✔✔Specialized control panel inside cabinet door
(coordinated, flash, etc)
✔✔What supports signal heads on span wire? -✔✔Messenger wire
✔✔What cabinet device acts as an interface device between the controller and the field
terminals? -✔✔Load switch
✔✔What cabinet device switches the traffic signals between a flash state and normal
operation? -✔✔Flash Transfer Relay
, ✔✔What cabinet device facilitates communications between the field terminals, the
detection devices and the MMU? -✔✔b) Bus Interface Unit
✔✔The MUTCD states that the flashing output on a flasher must be _____ per minute?
-✔✔b) 50-60
✔✔What unit is described as the brain of the traffic signal system? -✔✔c) Controller
✔✔It is recommended that a CMU/MMU get tested & recertified ________? -
✔✔Annually
✔✔Types of conduit -✔✔Types of conduit: (Rigid metallic conduit)
• GRC - Galvanized Rigid Conduit (thickest, threaded)
• IMC - Intermediate Metallic Conduit (thinner, threaded)
• EMT - Electrical Metal Tubing (thin, cannot be threaded)
Types of conduit: (Rigid non-metallic
conduit)
• PVC - Polyvinyl Chloride (wall thickness based on schedules, 20, 40, 80. Higher #
thicker wall)
• HDPE - High-Density Polyethylene (Poly pipe) (thickness based on SDR standard
dimension ratio, higher # thinner wall)
✔✔What percent of traffic accidents occur during overnight hours? -✔✔50%
✔✔Single conduit -✔✔360 degrees of total bend
✔✔Pull box -✔✔Tier rating, tier 8 box = 8000 pounds
✔✔Two types of cable jacketing -✔✔IMSA 19-1 spec (PVC jacket)
IMSA 20-1 spec (Polyethylene jacket, PE)
✔✔IMSA conductor sizes -✔✔IMSA conductors are available in #10
awg. To #16 awg. wire sizes.
• #12 & #14ga. wire is typically used in
traffic signals.
✔✔Typical cable counts -✔✔2: White
3: Red
4: Green
5: Orange
7: White (black tracer)
11: Blue (black tracer)
19: Blue (red tracer)
21: Orange (green tracer)
AND ANSWERS SURE A+
✔✔Ped heads mounting -✔✔Between 7 to 10 ft from bottom of head to sidewalk level
✔✔Ground fault circuit interruptor (GFCI) -✔✔Protect devices and workers from eletrical
shock. Trip with overload in 1/40th of second. Never plug cabinet equipment into GFCI
✔✔Mercury Contractor -✔✔Supply AC power to load switches. Being replaced with
SSRs (solid state) or hybrid relays
✔✔Signal phase locations -✔✔min 40', max 180'. If longer than 180' need supplemental
signal head
✔✔Fan/thermostat -✔✔Heat dissipation temp regulation 85-165 (170) moisture control
✔✔Communication components -✔✔Allow cabinet to connect with centralized
management system or other devices
✔✔UPS -✔✔Uninterruptable power supply aka battery backup
✔✔Maintenance switch panel -✔✔Specialized control panel inside cabinet door
(coordinated, flash, etc)
✔✔What supports signal heads on span wire? -✔✔Messenger wire
✔✔What cabinet device acts as an interface device between the controller and the field
terminals? -✔✔Load switch
✔✔What cabinet device switches the traffic signals between a flash state and normal
operation? -✔✔Flash Transfer Relay
, ✔✔What cabinet device facilitates communications between the field terminals, the
detection devices and the MMU? -✔✔b) Bus Interface Unit
✔✔The MUTCD states that the flashing output on a flasher must be _____ per minute?
-✔✔b) 50-60
✔✔What unit is described as the brain of the traffic signal system? -✔✔c) Controller
✔✔It is recommended that a CMU/MMU get tested & recertified ________? -
✔✔Annually
✔✔Types of conduit -✔✔Types of conduit: (Rigid metallic conduit)
• GRC - Galvanized Rigid Conduit (thickest, threaded)
• IMC - Intermediate Metallic Conduit (thinner, threaded)
• EMT - Electrical Metal Tubing (thin, cannot be threaded)
Types of conduit: (Rigid non-metallic
conduit)
• PVC - Polyvinyl Chloride (wall thickness based on schedules, 20, 40, 80. Higher #
thicker wall)
• HDPE - High-Density Polyethylene (Poly pipe) (thickness based on SDR standard
dimension ratio, higher # thinner wall)
✔✔What percent of traffic accidents occur during overnight hours? -✔✔50%
✔✔Single conduit -✔✔360 degrees of total bend
✔✔Pull box -✔✔Tier rating, tier 8 box = 8000 pounds
✔✔Two types of cable jacketing -✔✔IMSA 19-1 spec (PVC jacket)
IMSA 20-1 spec (Polyethylene jacket, PE)
✔✔IMSA conductor sizes -✔✔IMSA conductors are available in #10
awg. To #16 awg. wire sizes.
• #12 & #14ga. wire is typically used in
traffic signals.
✔✔Typical cable counts -✔✔2: White
3: Red
4: Green
5: Orange
7: White (black tracer)
11: Blue (black tracer)
19: Blue (red tracer)
21: Orange (green tracer)
