Traffic signal warrants on the PE Civil Transportation exam

A warrant problem on the Transportation exam gives you counts, a lane layout, a speed and sometimes a crash history, and asks whether a warrant is met or what volume would meet it. It all comes from the MUTCD, Part 4; the Handbook doesn't cover warrants. The MUTCD lists nine: eight-hour and four-hour vehicular volume, peak hour, pedestrian volume, school crossing, coordinated signal system, crash experience, roadway network, and intersection near a grade crossing. Meeting one does not, by itself, require a signal. The work is reading, in the right order.

What you actually need to own

• The shape of a volume check. Compare the major-street volume, as the total of both approaches, with the more critical minor-street approach, one direction only, hour by hour. The eight-hour warrant uses a table. The four-hour and peak-hour warrants use curves, and the point (major, minor) has to plot above the curve.
• Picking the column or figure first. If the major street's posted or 85th-percentile speed is above 40 mph, or the site is in an isolated community of under 10,000, the MUTCD allows the reduced (70 percent) set in place of the full volumes. That can flip the result. In one practice problem, a 45-mph major street fails at the full volumes and passes at the reduced ones. The pedestrian warrant has its own speed trigger; don't carry 40 mph over.
• Picking the row or curve. Count lanes for moving traffic on each approach: two lanes on a two-way street is one per approach.
• Alternatives inside a warrant. In the eight-hour warrant, Condition A (minimum vehicular volume) and Condition B (interruption of continuous traffic) each satisfy it on their own. The combination at the 80 percent volumes is for sites where neither one holds, and only after other remedies have been tried and failed.
• Conjunctive warrants. The crash warrant needs all of its parts: a failed trial of alternatives, a crash count, and a volume condition at reduced levels. Peak-hour Category A needs the delay, the approach volume and the total entering volume together.
• The hour. Any four consecutive 15-minute periods can count as one hour, if the hours don't overlap and major and minor volumes share the same hour. A rolling hour can beat the clock hour.
• Adjusting the counts first.
  • Minor-approach right turns that enter with minimal conflict come out of the minor-street volume, which can make it a one-lane approach.
  • With heavy major-street left turns, the higher left-turn volume may stand in as the "minor-street" volume, against the single opposing direction as the "major-street" volume.
  • The grade-crossing warrant applies adjustment factors to the minor-street volume before you read its chart.

Where people lose points

• Treating the higher-volume minor approach as the critical one. The critical approach is the one that meets its own lane row. A quieter one-lane approach can qualify where a busier two-lane approach opposite it fails.
• Misreading the lower threshold printed beside a curve. It governs only where the curve has flattened, at high major-street volumes. Below that, the curve sets the requirement.
• Counting crashes the warrant doesn't count. Read which crash types and which period apply. In one practice problem, a stack of rear-end crashes is the distractor.
• Reading the school-crossing gap test backward. It looks for fewer adequate gaps than there are minutes in the crossing period.
• Grade-crossing curves. Use the curve for the clear storage distance nearest the actual one, not the next larger. Take each adjustment factor from the actual distance and the minor-street approach.
• Spacing guardrails. The coordinated-system and pedestrian warrants each have a minimum spacing below which they shouldn't be applied, with different distances.

A note on standards

The exam supplies the 2009 MUTCD through March 2027 and the MUTCD 11th edition from April 2027. Work the warrants from the edition you'll be given. See the April 2027 change.

How to study it

Build one count sheet: 12 hours, a lane sketch and a speed. Run it through the eight-hour, four-hour and peak-hour warrants, then change one thing at a time: the speed across 40 mph, the right turns removed, a rolling hour. Before each lookup, write the column or figure, the row or curve, and the critical approach. Once a signal is justified, the timing follows: yellow change and red clearance.

Part of the Traffic Signals area of the PE Civil Transportation exam. → Start practicing free — the whole practice bank, free with an account.