Work-Zone Merging Taper Length and Device Count (MUTCD)
MUTCD merging-taper length for a lane closure and the channelizing devices it takes.
Example
You enter
- Lateral offset / lane width (ft) 12
- Posted / operating speed (mph) 55
- Channelizing device spacing (ft) 40
You get
- Taper length (ft) 660
- Channelizing devices 18
Details, formula, and sources
For 40 mph or less L = W x S^2 / 60, for 45 mph or more L = W x S; devices = ceil(L / spacing) + 1. Closing a 12 ft lane at 55 mph needs a 660 ft taper and 18 cones at 40 ft spacing; at 30 mph the taper shortens to 180 ft (6 devices) because the low-speed branch uses the speed squared. The low- and high-speed branches are a deliberate step. Shifting, shoulder, and downstream tapers use fractions of L.
taper_length_ft = speed_mph <= 40 ? offset_width_ft x speed_mph^2 / 60 : offset_width_ft x speed_mph; devices = ceil(taper_length_ft / device_spacing_ft) + 1.
MUTCD merging-taper identity by name (L = W S^2/60 for S <= 40, L = W S for S >= 45); first-principles device-count arithmetic.
The MUTCD merging-taper relation is public-domain federal guidance; the device spacing comes from the traffic-control plan.
Estimate. AHJ and licensed professional govern.
Field names used by the API: offset_width_ft, speed_mph, device_spacing_ft, taper_length_ft, devices
- Speed branch L = W S^2/60 for 40 mph or less, L = W S for 45 mph or more (MUTCD)MUTCD
- Device spacing channelizing-device spacing in a taper roughly the speed in feet (entered here)traffic-control plan