Planning & Estimating Traffic Control

Planning is where the C-31 exam starts: you read or design a traffic control plan, check it against the California MUTCD, and estimate the devices, labor, and layout a job needs.

The four areas of a TTC zone

Every temporary traffic control (TTC) zone is built from four areas, in the direction of travel:

1. Advance warning area — where drivers are told what is ahead.
2. Transition area — where drivers are moved out of their normal path, using a taper.
3. Activity area — the work itself: the work space, the traffic space, and the buffer space.
4. Termination area — where drivers return to their normal path (END ROAD WORK).

Tapers and buffer space

The transition area uses a taper whose length L depends on speed and how far the lane shifts:

Worked examples: a 12-ft lane shift at 30 mph needs 12 × 30² / 60 = 180 ft; the same shift at 55 mph needs 12 × 55 = 660 ft. Notice the jump as the formula changes at 45 mph.

Advance warning sign spacing

How far apart the advance warning signs go depends on road type and speed — roughly 100 ft on a slow urban street, a few hundred feet on faster urban roads, 500 ft on rural highways, and 1,000 ft or more on freeways. Estimating a job means counting signs, channelizing devices (by their spacing), and the crew to install them.