Work Zone Taper Length: How Long Should a Traffic Control Taper Be?
How long should a work zone taper be? It is one of the most important questions when setting up a temporary lane closure, traffic shift, or shoulder closure. A properly designed taper gives approaching drivers enough distance to recognize a change in the roadway and smoothly move from their normal travel path into the intended path. A taper that is too short can create an abrupt maneuver, while simply making a taper as long as possible is not necessarily the best solution. The Federal Highway Administration’s Manual on Uniform Traffic Control Devices (MUTCD) provides formulas and criteria for calculating work zone taper length based primarily on the speed of traffic, the amount of lateral offset, and the type of taper being used. This guide explains those formulas, provides practical examples, and includes taper-length charts for common roadway speeds and lane widths.Quick Answer: MUTCD Taper Length Formula
For speeds of 40 mph or less: L = WS² / 60 For speeds of 45 mph or more: L = WS Where:- L = taper length in feet
- W = width of the lateral offset in feet
- S = applicable speed in miles per hour
Important: These formulas calculate the value of L. Different types of tapers use different proportions of L.
What Is a Work Zone Taper?
A traffic control taper is a series of traffic cones, traffic drums, vertical panels, barricades, pavement markings, or other channelizing devices arranged to gradually move traffic out of or into its normal travel path. Tapers are commonly used to:- Close a traffic lane
- Shift traffic laterally
- Close a roadway shoulder
- Transition traffic into a one-lane section
- Return vehicles to their normal travel path
The Five Main Types of Work Zone Tapers
| Type of Taper | MUTCD Length Criterion | Typical Purpose |
|---|---|---|
| Merging Taper | At least L | Closes a lane and requires traffic to merge into another lane |
| Shifting Taper | At least 0.5 L | Moves traffic laterally while maintaining the same number of lanes |
| Shoulder Taper | At least 0.33 L | Closes or transitions traffic away from a shoulder |
| One-Lane, Two-Way Taper | 50 feet minimum to 100 feet maximum | Guides opposing traffic into a single lane used alternately in each direction |
| Downstream Taper | 50 feet minimum to 100 feet maximum | Helps return traffic to its normal lane or path after the work area |
How to Calculate Work Zone Taper Length
The MUTCD uses two different formulas depending on roadway speed.For Speeds of 40 MPH or Less
The formula is:L = WS² / 60
For example, assume traffic must move laterally by 12 feet on a road with a 30 mph applicable speed. W = 12 feet S = 30 mph L = (12 × 30²) / 60 L = (12 × 900) / 60 L = 180 feet A merging taper for that full 12-foot offset would therefore be at least approximately 180 feet long, before considering other site-specific factors.For Speeds of 45 MPH or More
The formula becomes:L = WS
For example, for a 12-foot lateral offset at 55 mph: L = 12 × 55 L = 660 feet The calculated value of L is therefore 660 feet. A merging taper would use at least L, while a shifting or shoulder taper would use the applicable proportion of L.Work Zone Taper Length Chart
The following table provides calculated merging taper lengths for 10-foot, 11-foot, and 12-foot lateral offsets at common roadway speeds. Values calculated from the MUTCD formulas have been rounded up to the next whole foot where necessary. The table is intended as a convenient planning reference; the actual lateral offset, traffic conditions, traffic-control plan, and applicable agency requirements must be considered for a specific project.| Speed | 10-Foot Offset | 11-Foot Offset | 12-Foot Offset |
|---|---|---|---|
| 20 mph | 67 ft | 74 ft | 80 ft |
| 25 mph | 105 ft | 115 ft | 125 ft |
| 30 mph | 150 ft | 165 ft | 180 ft |
| 35 mph | 205 ft | 225 ft | 245 ft |
| 40 mph | 267 ft | 294 ft | 320 ft |
| 45 mph | 450 ft | 495 ft | 540 ft |
| 50 mph | 500 ft | 550 ft | 600 ft |
| 55 mph | 550 ft | 605 ft | 660 ft |
| 60 mph | 600 ft | 660 ft | 720 ft |
| 65 mph | 650 ft | 715 ft | 780 ft |
| 70 mph | 700 ft | 770 ft | 840 ft |
| 75 mph | 750 ft | 825 ft | 900 ft |
Example: Taper Length for a 12-Foot Lane
A 12-foot lateral offset provides a useful example because 12 feet is a common lane width, but the same formulas work with any appropriate offset.| Speed | Merging Taper At Least L | Shifting Taper At Least 0.5L | 0.33L Reference* |
|---|---|---|---|
| 20 mph | 80 ft | 40 ft | 27 ft |
| 25 mph | 125 ft | 63 ft | 42 ft |
| 30 mph | 180 ft | 90 ft | 60 ft |
| 35 mph | 245 ft | 123 ft | 81 ft |
| 40 mph | 320 ft | 160 ft | 106 ft |
| 45 mph | 540 ft | 270 ft | 179 ft |
| 50 mph | 600 ft | 300 ft | 198 ft |
| 55 mph | 660 ft | 330 ft | 218 ft |
| 60 mph | 720 ft | 360 ft | 238 ft |
| 65 mph | 780 ft | 390 ft | 258 ft |
| 70 mph | 840 ft | 420 ft | 278 ft |
| 75 mph | 900 ft | 450 ft | 297 ft |
What Does W Mean in the Taper Formula?
W is the width of the lateral offset, measured in feet. This is an important distinction. W is not automatically the width of the entire roadway or even necessarily the full width of a traffic lane. If traffic is being moved laterally by an entire 12-foot lane, then W might be 12 feet. If traffic only needs to shift six feet, then W would be six feet.Example: 6-Foot Shift at 35 MPH
Using: W = 6 feet S = 35 mph L = (6 × 35²) / 60 L = (6 × 1,225) / 60 L = 122.5 feet Rounded up, L is approximately 123 feet. If this were a merging taper, the taper would be at least L. If it were a shifting taper, the MUTCD criterion is at least 0.5L.What Does S Mean?
For this MUTCD calculation, S represents the applicable speed in mph. The MUTCD describes S as the posted speed limit, the off-peak 85th-percentile speed before work begins, or the anticipated operating speed. Speed is especially important because it has a large effect on taper length. At lower speeds, the speed term is squared in the formula, while at 45 mph and above the calculation becomes W multiplied by S. The appropriate speed value for a particular traffic-control plan should be determined in accordance with the MUTCD and the requirements of the roadway owner or agency having jurisdiction.Merging Tapers
A merging taper is used when a lane is closed and drivers must merge into an adjacent lane. This generally requires the longest taper because vehicles from separate lanes need to merge into common road space. According to the MUTCD, a merging taper should be at least L and should provide drivers with adequate warning and enough distance to adjust speed and merge before reaching the downstream end of the transition. A merging taper might be formed using traffic cones, traffic drums, vertical panels, or other appropriate channelizing devices.Shifting Tapers
A shifting taper moves traffic laterally without eliminating a traffic lane. For example, construction might require two lanes to shift several feet to the left while both lanes remain open. The MUTCD taper criterion for a shifting taper is at least 0.5L. If the calculated value of L is 600 feet, for example: Shifting taper = 0.5 × 600 = at least 300 feet The actual alignment, available roadway width, curves, pavement markings, traffic volumes, and other field conditions still need to be considered.Shoulder Tapers
A shoulder taper can be used where a shoulder is being closed or where an improved shoulder might otherwise appear to drivers to be an available travel lane. The MUTCD criterion is at least 0.33L. However, if a shoulder is actually functioning as a travel lane, the MUTCD indicates that a normal merging or shifting taper should be used rather than the shorter shoulder-taper criterion.One-Lane, Two-Way Traffic Tapers
Some work zones require both directions of traffic to alternately use a single open lane. For this configuration, the MUTCD calls for a taper between 50 and 100 feet long, with channelizing devices at approximately 20-foot spacing to guide traffic into the one-lane section. A downstream taper is then used to help traffic return to its original lane. One-lane, two-way traffic operations can also require flaggers, temporary traffic signals, STOP or YIELD control, or other measures depending on the specific roadway and traffic-control plan.Downstream Tapers
A downstream taper occurs after the work area and can provide a visual cue that drivers may return to their original lane or path. When used, MUTCD guidance calls for a downstream taper between 50 and 100 feet long, with devices spaced at approximately 20 feet.Taper Length and Traffic Cone Spacing Are Different
This distinction causes a lot of confusion. Taper length determines the total distance over which traffic is moved laterally. Traffic cone spacing determines the distance between individual cones or other channelizing devices within that taper. For example, a merging taper might be 660 feet long, but that certainly does not mean cones should be placed 660 feet apart. Under general MUTCD guidance, the spacing between cones, tubular markers, vertical panels, drums, and barricades used for taper channelization should not exceed a distance in feet equal to the speed limit in mph. For tangent channelization, the general maximum is twice the speed limit in feet. We explain that subject in detail in our companion guide: Traffic Cone Spacing Guide: How Far Apart Should Traffic Cones Be?Example: 55 MPH Lane Closure
Consider a highway where a full 12-foot lane is being closed and traffic must merge into the adjacent lane. W = 12 feet S = 55 mph Because the speed is 45 mph or greater: L = WS L = 12 × 55 L = 660 feet The merging taper would therefore be at least approximately 660 feet under the basic MUTCD calculation. The individual traffic cones, drums, or other channelizing devices within that taper would then be placed according to the appropriate device-spacing guidance and the approved traffic-control plan.Example: 30 MPH Urban Lane Closure
Now consider a 12-foot lateral offset on a 30 mph roadway. Because the speed is 40 mph or less: L = WS² / 60 L = (12 × 30²) / 60 L = 180 feet The basic merging taper calculation is therefore 180 feet. An urban environment, however, can also contain intersections, driveways, parking entrances, crosswalks, transit stops, and short blocks. Those conditions may affect how a traffic-control plan is implemented.Is a Longer Taper Always Safer?
No. This is an important point that is sometimes overlooked. The MUTCD specifically notes that longer tapers are not necessarily better, particularly in urban areas where short block lengths, driveways, intersections, and similar features affect traffic. An unnecessarily long taper can encourage drivers to delay making a lane change. The goal is not simply to create the longest possible taper. The objective is to provide a clear, predictable transition that gives drivers sufficient warning and enough distance to make the required maneuver.What Traffic Control Devices Can Form a Taper?
A taper can be created using several types of channelizing devices depending on the roadway, speed, project duration, visibility requirements, and approved traffic-control plan.Traffic Cones
Traffic cones are highly portable and are widely used for temporary traffic control. Traffic Safety Store offers multiple sizes, base weights, colors, and reflective configurations for different applications.Traffic Drums
Traffic drums provide a larger visual target and are frequently used for highway construction and longer-duration work zones. Reflective sheeting provides enhanced nighttime visibility.Vertical Panels and Barricades
Traffic barricades and vertical panels can also be used for channelization where appropriate. Vertical panels are particularly useful where lateral space is limited.Construction Signs and Sign Stands
A taper is only one part of a temporary traffic control setup. Drivers generally need advance warning before reaching the transition. Traffic Safety Store carries roll-up construction signs and portable sign stands for temporary roadway applications.Other Factors That Can Affect Taper Design
The formulas provide an important starting point, but real-world temporary traffic control involves more than a single calculation. Factors that can affect a taper or traffic-control plan include:- Actual operating speed
- Traffic volume
- Lane width
- Amount of lateral offset
- Number of lanes being closed or shifted
- Roadway curves
- Intersections and interchange ramps
- Driveways and access points
- Sight distance
- Existing pavement markings
- Pedestrian and bicycle traffic
- Nighttime visibility
- Weather conditions
- Duration of the work
- State and local requirements
- The approved temporary traffic control plan
Advance Warning Comes Before the Taper
The transition area does not stand alone. Before drivers reach a taper, an appropriate advance warning area is generally needed to tell them what is changing ahead. Depending on the work zone, this might include legends such as:- ROAD WORK AHEAD
- RIGHT LANE CLOSED AHEAD
- LEFT LANE CLOSED AHEAD
- SHOULDER CLOSED
- ONE LANE ROAD AHEAD
- BE PREPARED TO STOP
Frequently Asked Questions About Work Zone Taper Length
What is the MUTCD formula for taper length?
For speeds of 40 mph or less, the MUTCD formula is L = WS² / 60. For speeds of 45 mph or greater, the formula is L = WS. L is taper length in feet, W is lateral offset in feet, and S is the applicable speed in mph.How long should a merging taper be?
A merging taper should be at least L as calculated using the MUTCD taper-length formula. For example, a 12-foot offset at 55 mph produces an L value of 660 feet.How long should a taper be at 30 mph?
It depends on the width of the lateral offset. For a 12-foot offset at 30 mph, L = (12 × 30²) / 60, which equals 180 feet. A merging taper would therefore be at least approximately 180 feet under the basic calculation.How long should a taper be at 40 mph?
For a 12-foot offset at 40 mph, the calculation is L = (12 × 40²) / 60, resulting in 320 feet.How long should a taper be at 45 mph?
For a 12-foot offset at 45 mph, L = 12 × 45, or 540 feet.How long should a taper be at 55 mph?
For a full 12-foot lateral offset at 55 mph, L = 12 × 55, or 660 feet. A merging taper uses at least L, while a shifting taper uses at least 0.5L.What is the difference between a merging taper and a shifting taper?
A merging taper removes a traffic lane and requires vehicles to merge into an adjacent lane. A shifting taper moves traffic laterally while maintaining the same number of travel lanes. Because merging traffic requires drivers to combine into common road space, the merging taper is longer.How long is a shoulder taper?
The MUTCD criterion for a shoulder taper is at least 0.33L. The correct calculation should use the actual width of the lateral offset involved in the shoulder closure.How long is a downstream taper?
If a downstream taper is used, MUTCD guidance specifies a minimum length of 50 feet and maximum length of 100 feet, with devices at approximately 20-foot spacing.How far apart should cones be within a taper?
Taper length and cone spacing are separate calculations. General MUTCD guidance states that the spacing between channelizing devices in a taper should not exceed a distance in feet equal to the speed limit in mph. See our complete traffic cone spacing guide for charts and examples.Does OSHA have work zone taper requirements?
OSHA provides highway work-zone safety requirements and resources and references the MUTCD for temporary traffic control practices involving signs, signaling, barricades, and related roadway traffic control. Employers should review applicable OSHA requirements in addition to MUTCD, state, local, and agency requirements.Build a Clear and Predictable Work Zone
Proper taper design helps drivers understand where they are expected to travel before they reach the work area. But taper length is only one component of an effective temporary traffic control zone. Advance warning signs, channelizing-device spacing, buffer space, nighttime visibility, worker protection, pedestrian accommodations, and the selection of appropriate traffic control devices all need to work together. Traffic Safety Store supplies a broad selection of professional traffic control equipment, including:- Traffic cones
- Traffic drums
- Traffic barricades and barriers
- Roll-up construction signs
- Portable sign stands
Authoritative Resources
- FHWA – Current Manual on Uniform Traffic Control Devices, 11th Edition with Revision 1
- OSHA – Highway Work Zones and Signs, Signals, and Barricades
Safety and compliance notice: This article is provided for general informational purposes only and is intended for a U.S. audience. The calculations and examples shown here are intended to explain general MUTCD taper concepts and are not a substitute for an approved temporary traffic control plan, engineering judgment, professional traffic-control design, or requirements established by a state, municipality, roadway owner, or other authority having jurisdiction. Conditions vary by roadway and project. Always consult the current MUTCD, applicable federal, state and local requirements, the authority having jurisdiction, and an approved traffic-control plan where required before establishing a work zone.