Traffic Signal Inspection and Field Verification
Scope of field verification
The exam tests whether you can confirm that a signal installation matches approved plans, specifications, and MUTCD geometry before acceptance. Inspection starts before energization: compare shop drawings, pole schedules, phasing, and detection layout to the field. Record measurements, not impressions.
Core checks
- Mounting height: overhead signal faces commonly 15–19 ft above pavement; post-mounted faces within plan and MUTCD limits and not obstructed by signs or foliage.
- Lateral placement and visibility: each approach has the required number of faces; primary faces are visible from the stopping point; backplates and visors reduce glare.
- Clearances: vertical clearance over travel lanes, pedestrian pushbutton reach, foundation elevation, and handhole orientation.
- Structure: anchor-bolt torque, pole plumb, span-wire tension, bonding, and grounding continuity.
- Operational: flash mode, pedestrian phases, conflict-monitor status, detection calls, and cabinet labeling.
Worked example
A plan requires the bottom of an overhead signal face at 17 ft above pavement. You measure 14 ft 8 in. from pavement to the bottom of the housing. Reject it: it is below the common 15-ft minimum, so tall vehicles could strike it and the face may fall outside the visibility envelope. The fix is to adjust the span or mast arm and re-measure, then document the corrected elevation with a photo.
Traps
Measuring from the curb or sidewalk instead of pavement; checking only the main-street approach; accepting a contractor as-built without field measurement; ignoring backplate condition; and recording a verbal pass without date, location, and instrument reading.