Idaho traffic control plan requirements

We have not yet verified which manual governs in this state. Figures shown are federal MUTCD 11th Edition, Revision 1 values. Taper length, channelizing device spacing and advance warning sign placement come from Part 6; individual cities layer their own submittal checklists on top.

What governs in Idaho

Provisional

We have not yet verified which manual governs in this state. Figures shown are federal MUTCD 11th Edition, Revision 1 values.

We have not read this state’s Part 6 directly, so the figures below are federal MUTCD values. Check them against the governing document before you submit.

Manual on Uniform Traffic Control Devices for Streets and Highways

Taper length for Idaho work zones

Enter the posted speed and the width of the lateral offset. The base length L comes from MUTCD 11th Edition Table 6B-4, with the taper-type criterion from Table 6B-3.

Posted speed

Posted speed limit, off-peak 85th-percentile speed prior to work starting, or anticipated operating speed.

Lateral offset (W)

How far traffic is moved sideways — usually the width of the closed lane.

Taper type

Open this in the plan builder

Merging taper length

245ft

L = W × S² ÷ 60 = 12 × 35² ÷ 60 = 245.0 ft

MUTCD 11th Ed, Tables 6B-3 and 6B-4 — at least L

Plan view

8 devices at 35 ft

Length is to scale; the lateral offset is exaggerated so the taper is legible.

All taper types at these conditions

MUTCD 11th Ed, Tables 6B-3 and 6B-4

Merging taper

at least L

245 ft

Shifting taper

at least 0.5 L

125 ft

Shoulder taper

at least 0.33 L

85 ft

One-lane, two-way traffic taper

50 ft min, 100 ft max

50 ft

Downstream taper

50 ft min, 100 ft max

50 ft

Channelizing devices

MUTCD 11th Ed, Section 6K.01

Maximum spacing in this taper

1 × 35 mph

35 ft

Devices required

One at each end, evenly spaced between

Table 6B-3 states these lengths as minimums. Longer tapers are not automatically better — MUTCD Section 6B.08 notes that extended tapers tend to encourage sluggish operation and delay lane changes, particularly in urban areas with short blocks or frequent driveways.

No Idaho agency checklists documented yet

Conemap documents each agency's published requirements from its own source document, dated and cited. If your city publishes a traffic control plan checklist, send it to hello@conemap.com and it will be added.