Traffic Signal Construction and Installation
From stakeout to substantial completion
Construction questions focus on sequence, inspection hold points, and the tolerances an inspector must enforce.
Before excavation: 811 utility locate, approved MOT plan per MUTCD Part 6, permits, and a pre-construction meeting that fixes hold points. Know conduit installation: rigid or PVC conduit at the specified cover depth, sweeps instead of field bends, mandrel and pull-line installed, and ends capped until cable is pulled. Know pull box practice - spacing limits on straight runs, limits on the number of bends between boxes, and drainage. Conduit fill should not exceed roughly 40 percent of the conduit cross-section.
Foundations: anchor bolt templates set to the bolt circle and projection dimensions, concrete per the mix design, and adequate cure before loading a mast arm. Poles go up plumb; span wire is tensioned to the specified sag (commonly a small percentage of span length) so heads do not sway or drift out of aim. The cabinet sits on a level pad, outside the clear zone, with the door swinging away from traffic and adequate working clearance.
Grounding and bonding: ground rod, grounding electrode conductor, and bonding of poles, cabinet, and metallic conduit. Service equipment includes a disconnect, overcurrent protection, and surge protection.
Testing and commissioning: point-to-point wiring check, insulation resistance, detection call verification at the cabinet, conflict-monitor and flash-transfer test, timing verification, and an as-built package.
Traps: applying the wrong standard (NESC governs line-side and span work; NEC governs the service and cabinet wiring); skipping hold-point inspections; accepting a punch list without a completed detection test.
Rule of thumb: a pull box at every 300 ft of straight run and at no more than two 90-degree bends - always confirm against the project spec.