How to Build a Temporary Traffic Control Plan: Tapers, Buffers and Sign Spacing
A step-by-step guide to a work-zone traffic control plan under MUTCD Part 6: choosing the typical application, taper length formulas, buffer space, advance warning sign spacing and devices.
A temporary traffic control (TTC) plan — usually just called a traffic control plan or TCP — shows how drivers, pedestrians, cyclists and workers will move safely through or around a work zone. In the United States, TTC is governed by Part 6 of the Manual on Uniform Traffic Control Devices (MUTCD), now in its 11th Edition, plus any state supplement or state MUTCD.
This guide walks through the core decisions in a TCP. Always confirm values against the edition and state supplement your agency has adopted.
The parts of a work zone
Every TTC zone has the same four areas, in the order a driver meets them:
- Advance warning area — signs that tell drivers what’s ahead
- Transition area — tapers that move traffic out of its normal path
- Activity area — the buffer space and the work space itself
- Termination area — where traffic returns to normal, with an optional downstream taper and END ROAD WORK sign
Step 1: Choose the typical application
The MUTCD’s typical applications are the starting point: lane closure on a two-lane road with flaggers, lane closure on a multilane road, lane closure near the side of an intersection, shoulder work, sidewalk closure and pedestrian detour, and many more. Pick the one that matches the road type, the closure, the duration and the speed — then adapt it to the real road, including driveways, cross streets and pedestrian routes the typical application doesn’t show.
Step 2: Compute the taper length
The merging taper length L depends on the speed and the width of the offset:
- Speed 40 mph or less: L = W × S² ÷ 60
- Speed 45 mph or more: L = W × S
where W is the width of offset in feet and S is the posted speed, the off-peak 85th-percentile speed before work starts, or the anticipated operating speed, in mph.
For a 12-foot lane at 45 mph: L = 12 × 45 = 540 feet.
Other tapers are fractions of L:
| Taper type | Length |
|---|---|
| Merging taper | at least L |
| Shifting taper | at least ½ L |
| Shoulder taper | at least ⅓ L |
| One-lane, two-way taper | 50 ft minimum, 100 ft maximum |
| Downstream taper | 50 ft minimum, 100 ft maximum per lane |
Step 3: Set the buffer space
The longitudinal buffer between the end of the taper and the work space gives an errant vehicle room to stop. Its length is based on stopping sight distance for the speed — for example, about 360 feet at 45 mph. Equipment, materials and vehicles shouldn’t be stored in the buffer.
Step 4: Space the advance warning signs
Advance warning signs are spaced by road type. The commonly used distances between signs (A, B and C) are:
| Road type | A (ft) | B (ft) | C (ft) |
|---|---|---|---|
| Urban, low speed (≤ 40 mph) | 100 | 100 | 100 |
| Urban, high speed (≥ 45 mph) | 350 | 350 | 350 |
| Rural | 500 | 500 | 500 |
| Expressway / freeway | 1,000 | 1,500 | 2,640 |
Cross streets inside the work zone need their own warning — typically a ROAD WORK AHEAD sign on each approaching cross street.
Step 5: Place channelizing devices
Cones, tubular markers, drums or barricades define the taper and the edge of the work area. Device spacing in feet should generally be no more than the speed in mph in tapers, and no more than twice the speed in tangent sections — for example, 45-foot spacing in a 45 mph taper. Add an arrow board for lane closures on multilane, higher-speed roads.
Step 6: Accommodate pedestrians and cyclists
If the work affects a sidewalk, crosswalk or bike lane, the plan must provide an accessible alternate route that matches the existing route’s accessibility as closely as possible — not just a SIDEWALK CLOSED sign. Detectable channelizing devices are needed where pedestrians are guided around work.
Step 7: Check what the typical doesn’t show
- Driveways and business access inside the work zone
- Signal heads, detectors and pedestrian push buttons affected by the closure
- Sight distance around curves and crests to the first sign
- Work hours and restrictions (often required by permit)
- Flagger stations, if used, and their sight distance
Step 8: Produce the sheets
A permit-ready plan set usually includes a title block, plan sheets with stationing and match lines, a sign legend with quantities, general notes, and detour plans where needed.
Automating the mechanics
The calculations above are deterministic, which makes them ideal to automate — but applying them to a real road with driveways, cross streets and bike lanes still needs care. In LaneMarker AI Studio, you mark the work area and the plan is drafted on the traced road: typical application selected, tapers, buffer and sign spacing computed from the speed, devices placed, and every value cited. When a driveway sits inside the work area, it stops and asks. California MUTCD and Caltrans standard plans are built in. And before submittal, LaneMarker PlanCheck can review the set against your local supplement.