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Idaho Multilane Lane Closure Traffic Control Plan
Close one lane of a four-or-more-lane, non-divided road and traffic merges past the work behind a taper and an arrow board — MUTCD TA-30. The merging taper is the long one, and it grows fast with speed. Here is what the engine computes for Idaho at 25, 35, 45, and 55 mph.
Real MUTCD dimensions, a title block, and a printable sheet — no account, no cost.
Build this plan free — takes about 2 minutesComputed MUTCD dimensions
Governing typical application: TA-30 — Lane Closure on a Multilane Street. Assumptions: urban collector, 4 through lanes, 12 ft lanes, 12 ft lateral offset, 100 ft work space, short-term duration. Rule set MUTCD 11th Ed. + 50-state/DC adoption layer + ID/ACHD profiles, rule set 2026-08 rev 4.
| Posted speed | Taper length (merging) | Advance signs A / B / C | Longitudinal buffer | Device spacing taper / tangent | Channelizing devices |
|---|---|---|---|---|---|
| 25 mph | 125 ft | 100 ft / 100 ft / 100 ft | 155 ft | 25 ft / 50 ft | 18 |
| 35 mph | 245 ft | 250 ft / 250 ft / 250 ft | 250 ft | 35 ft / 70 ft | 18 |
| 45 mph | 540 ft | 350 ft / 350 ft / 350 ft | 360 ft | 45 ft / 90 ft | 24 |
| 55 mph | 660 ft | 350 ft / 350 ft / 350 ft | 495 ft | 55 ft / 110 ft | 23 |
What applies in Idaho
- Agency rule set
- State of Idaho (MUTCD as adopted)
- MUTCD adoption
- National MUTCD adopted with a state supplement (cross-checked against a second source)
Printed on every Idaho sheet:
- Idaho has adopted the national MUTCD for use on Idaho highways and streets; the national Part 6 requirements apply unless the local highway authority has modified them.
This rule set holds no Idaho-specific permit form, review time, or closure-hour restriction, so none is shown. Those are set by whoever owns the road — state DOT, county, city, or highway district — and have to come from them.
Governing citation: Idaho Code §49-201(3) — the Idaho Transportation Board shall adopt a manual of traffic-control devices correlating with and conforming to the most recent edition of the national MUTCD; implemented by IDAPA 39.03.41 “Rules Governing Traffic Control Devices,” which adopts the MUTCD for use in Idaho. See also Idaho Code §49-209 (local traffic-control devices) for city and highway-district authority, and the ITD Traffic Manual Idaho Supplement for state-highway modifications.
Questions people actually ask
How long is the merging taper for a lane closure in Idaho?
It depends on posted speed and the width being closed. MUTCD uses L = W·S²/60 below 45 mph and L = W·S at 45 mph and above. The table above computes it for a 12 ft lane at four speeds; the builder recomputes it for your actual lane width.
Do I need an arrow board?
For a stationary lane closure on a multilane road, yes — the arrow board goes at the beginning of the merging taper. It supplements the channelizing devices and the advance signs; it does not replace either.
Does this cover freeway and divided-highway closures?
No, and the tool refuses rather than approximating. TA-30 assumes a non-divided two-way road with four or more through lanes. Divided highways and freeways run off their own plates and need a sheet designed for them.
Real MUTCD dimensions, a title block, and a printable sheet — no account, no cost.
Build this plan free — takes about 2 minutesDISCLAIMER — READ BEFORE USE
This traffic control plan was generated by an automated tool for planning and reference purposes only. It is based on the MUTCD 11th Edition Part 6 typical applications and the agency rule set selected above. It is not a certified, sealed, or professionally engineered document and has not been reviewed against actual field conditions at this site. It must be reviewed, adapted to field conditions, and approved by a qualified person — and, where required, by the permitting agency and/or a licensed Professional Engineer — before use. Field conditions govern. The user is solely responsible for work-zone safety, for conformance with all applicable federal, state, and local requirements, and for obtaining all required permits. PM Axsus disclaims all liability arising from use of this document.