Traffic Signal Installation and Construction
Installation questions reward knowing the sequence and the inspection points that follow from it. Before excavation, call for utility locates and confirm that foundation elevations match the plan; a foundation poured at the wrong grade cannot be fixed by adjusting the arm. Concrete must reach specified strength before poles or span wire are loaded. Span-wire installations depend on messenger tension, sag, and backstays; mast-arm installations depend on anchor-bolt torque and arm leveling.
Conduit and cable work is where most inspection failures occur. Verify trench depth and bedding, use sweep bends matched to conduit size, keep conduit ends capped until pulling, and tag every conductor at both ends against the cable schedule. Leave a drip loop at weatherheads and slack at pull boxes. Bond all metallic parts - poles, cabinet, controller, and ground rod - into a single grounding electrode system.
Testing before turn-on: point-to-point continuity, insulation resistance with a megger, verification of each lamp or LED output from the controller, and a detection test with a vehicle or loop tester. Document results; the functional test record is your evidence at acceptance.
Traps: confusing mounting height with clearance height; assuming conductor color identifies function when the specification requires tags; forgetting that a phasing revision can change field wiring.
Worked example: conduit fill. For three or more conductors, the NEC limits fill to 40 percent of interior area. A 2-inch conduit with about 3.14 in-sq of interior area leaves roughly 1.26 in-sq usable.