8.3 Curbs, Sidewalks, Curb Ramps (ADA), Guardrail, Utilities, Signals & Lighting

"Incidental" construction items — curb and gutter, sidewalk, curb ramps, guardrail, sign and signal foundations, striping — rarely carry the pay-item weight of earthwork or pavement, but they are exactly the items the traveling public interacts with directly, and they carry their own hard tolerances that an inspector cannot wave through as minor.

Curb and Gutter, Sidewalk & Curb Ramps

Curb and gutter sections are checked for line, grade, cross slope, and joint spacing the same way a concrete pavement is — a curb that meets grade at the beginning and end of a run but wanders in between will pond water at the low spots instead of carrying it to the nearest inlet. Sidewalk panels follow similar grade and cross-slope controls, plus jointing and curing requirements consistent with the concrete-flatwork practices covered in Chapter 5.

Curb ramps carry the tightest tolerances in this group because they are governed by accessibility law, not just by the project specification. Under current ADA/PROWAG accessibility criteria:

• Running slope (the slope in the direction of travel, down the ramp) is limited to 1:12, or 8.33% maximum.
• Cross slope (side-to-side, perpendicular to travel) is limited to 1:48, or about 2% maximum — far flatter than the running-slope limit, and a separate measurement the inspector has to check independently.
• Side flares, where used instead of returned curbs, are limited to 1:10 maximum.
• A detectable warning surface (truncated domes) is required at the bottom landing so the ramp is identifiable underfoot and by cane.
• A minimum clear width and a level landing at the top and bottom of the ramp are required so a wheelchair user has room to maneuver onto the ramp rather than turning on a slope.

A ramp that is a fraction of a degree over 8.33% running slope fails, even if it is short, even if the surrounding sidewalk is otherwise compliant, and even if the contractor built it to match existing grade. Because these tolerances are legal minimums rather than project preferences, the inspector checks them with a digital level or smart level on every ramp, not by eye.

Guardrail

Modern W-beam guardrail on new construction is built to MASH (Manual for Assessing Safety Hardware) crash-test criteria, most commonly using the Midwest Guardrail System (MGS). The MGS mounts the top of the W-beam rail at 31 inches above the roadway or shoulder surface — a full 4 inches higher than the older 27-inch standard it replaced — with deeper, 12-inch offset blocks between the rail and the posts. Height tolerance depends on the standard referenced by the project, but many MGS specifications allow the rail to run from 31 inches down to roughly 28 inches without requiring an adjustment, while flagging installations outside that band for correction. The inspector verifies rail height, post spacing, post embedment depth, splice location (mid-span between posts, not at the post itself, for MGS), and terminal-end hardware against the plan detail sheet — guardrail that "looks about right" from the road is not the same as guardrail that will perform in a crash test the way it was designed to.

Utility Coordination and Locate Marking

Highway projects routinely cross or run parallel to underground utilities that are not part of the contract but that construction activity can damage. Before any excavation near a known or suspected facility, the utility owner (or a one-call/811 locate service) marks the ground with temporary paint or flags following the nationwide APWA Uniform Color Code:

The inspector confirms that locate marks are present and current before excavation starts near a marked facility, that the contractor is hand-exposing (potholing) rather than blind-digging within the tolerance zone around a marked line, and that any conflict between the plans and an actual utility location as found in the field is reported up the chain rather than worked around informally.

Signals, Lighting & Signage

Traffic signal poles, lighting standards, and large sign structures are incidental-construction items with their own foundations (drilled shaft or spread footing, sized and reinforced per the structural detail), anchor-bolt patterns, grounding, and conduit runs for wiring — all of which the inspector checks before the pole ever goes up, since a foundation defect is far harder to correct after the structure is standing. Regulatory and warning signs follow MUTCD mounting-height rules: a minimum of 7 feet from the top of curb to the bottom of the sign in urban areas with sidewalks (to clear pedestrians), versus a minimum of 5 feet from the roadway surface in rural areas without curb or sidewalk. Pavement markings and striping are checked for correct material, width, and retroreflectivity, and — like every other incidental item in this section — for whether they were actually built to the plan detail rather than to "what looks reasonable in the field."