Work Zone Advance Warning Sign Spacing (MUTCD 6C-1)
How far ahead of a work-zone taper the advance warning signs go, per MUTCD Table 6C-1.
Example
You enter
- Road type rural
- Signs in the series (1-3) 3
- Speed limit (mph, 0 = skip the 8-12x check) 55
You get
- A (ft) 500
- B (ft) 500
- C (ft) 500
- First sign (ft) 1500
- Advance warning area begins 1500
- Speed rule min (ft) 440
- Speed rule max (ft) 660
Details, formula, and sources
MUTCD Table 6C-1 verbatim (a public-domain federal work): urban low 100/100/100, urban high 350/350/350, rural 500/500/500, expressway 1,000/1,500/2,640 ft. Reported as distances UPSTREAM of the transition, because the series reads backward from how it is signed - the third sign is the first a driver sees, so a rural three-sign series opens 1,500 ft ahead of the taper. Adds the 8-12x speed-limit placement check and the 1,500-ft open-highway guidance.
Table 6C-1 A/B/C spacings by road type: urban low 100/100/100, urban high 350/350/350, rural 500/500/500, expressway 1,000/1,500/2,640 ft; sign positions upstream of the transition = A, A+B, A+B+C.
MUTCD Table 6C-1, Suggested Advance Warning Sign Spacing, from the FHWA Manual on Uniform Traffic Control Devices - a US-government public-domain work, extracted from the FHWA PDF rather than a secondary summary.
The MUTCD is published free at mutcd.fhwa.dot.gov and is in the public domain.
Estimate. AHJ and licensed professional govern.
Field names used by the API: road_type, sign_count, speed_mph, a_ft, b_ft, c_ft, first_sign_ft, total_ft, speed_rule_min_ft, speed_rule_max_ft
- Public-domain table MUTCD Table 6C-1 reproduced verbatim; it is a US-government work, not a copyrighted tableFHWA MUTCD Table 6C-1
- A/B/C direction A is transition-to-nearest-sign; the third sign is the first a driver seesMUTCD Table 6C-1 footnote
- Rural placement guidance first warning sign 8 to 12 times the speed limit in mph; area 1,500 ft or more on open highwayMUTCD 6C.04