Channelizing Device Spacing Explained: How Far Apart Cones, Drums and Barricades Go

The rule for how far apart to set cones is one of the shortest in the manual. It is also one of the most often applied backward, with crews treating a maximum as a target and stretching devices as far apart as the rule appears to allow.

This guide explains the national guidance on spacing for channelizing devices, the places where the manual asks for closer spacing, how to turn spacing into a device count, and the field errors that inspectors notice. For what each device is and when to use it, see our explainer on channelizing devices.

Everything here refers to Part 6 of the MUTCD 11th Edition, with the current revision listed on FHWA's 11th Edition page. States adopt the manual with changes, and many state manuals and standard sheets give their own spacing tables. The plan and the state standard govern on a real job.

The general rule

Section 6K.01 gives the guidance in a single paragraph. For cones, tubular markers, vertical panels, drums and barricades:

• In a taper, spacing should not exceed a distance in feet equal to 1 times the speed limit in mph.
• On a tangent, spacing should not exceed a distance in feet equal to 2 times the speed limit in mph.

A tangent here means the straight run of devices alongside the buffer and the work space, after the taper has finished moving traffic over.

So for common speeds:

| Speed limit | Maximum taper spacing | Maximum tangent spacing | | --- | --- | --- | | 25 mph | 25 feet | 50 feet | | 35 mph | 35 feet | 70 feet | | 45 mph | 45 feet | 90 feet | | 55 mph | 55 feet | 110 feet | | 65 mph | 65 feet | 130 feet |

Those figures are simply the rule applied. Two things about the wording matter.

It is guidance, expressed as "should." And it is a ceiling: "should not exceed." Nothing in the manual discourages setting devices closer together, and several provisions encourage it.

Why tapers are tighter

In the taper, the devices are doing the hardest job in the setup. They form a diagonal line that a driver has to read as "this lane is ending, move over." Gaps in that line look like openings. A driver who is late, distracted or following a truck sees a space between two cones and takes it.

On the tangent the message has already been delivered. The devices are marking an edge, not asking for a maneuver, and a longer interval still reads as a continuous line at speed.

That logic also explains why the short tapers get their own figure. A one-lane, two-way traffic taper and a downstream taper are each 50 to 100 feet long under Section 6B.08, and the guidance is devices at approximately 20-foot spacing. At 55 mph the general taper rule would allow 55 feet between devices, which would leave a 50-foot taper with two cones. Twenty feet makes the short taper read as a taper. See taper length and buffer space for how the taper lengths themselves are calculated, and one-lane, two-way traffic control methods for where the short taper is used.

Where the manual asks for closer spacing

The general rule is the starting point. The manual tightens it in specific situations.

When devices stand in for pavement markings. The notes to the typical applications for lane shifts say that where channelizing devices are used instead of pavement markings, the maximum spacing should be one half of S feet, where S is the speed in mph. At 60 mph that is 30 feet, a quarter of the general tangent figure.

When old markings conflict with the temporary path. For short-term and intermediate-term projects where removing conflicting markings is impracticable, the same half-S maximum applies through the area of conflict. One of those notes puts it as a requirement: where it is not feasible to remove and restore markings, channelization shall be made dominant by using a very close device spacing. The devices have to overpower paint that is telling drivers something else. See temporary pavement markings in work zones.

When devices form a temporary center line. Section 6N.11 says that when it is necessary to create a temporary center line that is not consistent with the pavement markings, channelizing devices should be used and closely spaced.

Near an open ramp. Where devices run along the mainline past an exit that remains open, the notes say the spacing should be reduced in the vicinity of the off ramp to emphasize the opening.

When conditions are complex. Section 6N.03 lists more channelizing devices at closer spacing among the additions to consider when a site is more complicated than the typical application it is based on, and says device spacing may be adjusted to provide additional reaction time.

Past the end of a transition. This one is about extent, not interval. Where devices could lead traffic out of the intended space, Section 6K.01 says they should be extended a distance in feet of 2 times the speed limit in mph beyond the downstream end of the transition area.

For pedestrians. A line of cones at 40-foot intervals is not a pedestrian barrier. Pedestrian channelization has its own requirements for continuity and detectability. See pedestrian accommodation in work zones.

Warning lights follow the devices. Where lights are used on channelizing devices, the guidance in Section 6L.07 is that their maximum spacing should be identical to the channelizing device spacing requirements. See barricade lights and warning light types.

Which speed to use

The spacing rule refers to the speed limit. Taper length is calculated from the posted speed limit, the off-peak 85th-percentile speed before work starts, or the anticipated operating speed, as the manual's taper table notes.

In practice the plan or the state standard sheet will state the spacing, and you build to that. Where you are working from a typical application without a site-specific plan, be cautious about using a reduced work zone speed limit to justify wider spacing or a shorter taper if traffic is not actually slowing. If drivers are arriving at 60, a taper built for 45 is short and sparse. Raise it with whoever is responsible for the plan.

Counting devices

Spacing is what turns a drawing into a load list. The arithmetic is short and worth doing before the truck leaves, not at the roadside.

For each run of devices:

number of devices = length divided by spacing, rounded up, plus one

The plus one is the device at the start of the run.

A worked example, with figures chosen only to show the method. A right-lane closure at a 45 mph speed limit with a 12-foot lane. The merging taper is 12 times 45, or 540 feet. At 45-foot spacing that is 12 intervals, so 13 devices. A buffer and work space totaling 800 feet at 90-foot tangent spacing is 9 intervals rounded up, so 10 devices, of which the first is shared with the end of the taper, leaving 9 more. A downstream taper of 100 feet at 20-foot spacing is 5 intervals, 6 devices, one shared, so 5 more. Total: 27, before spares.

Then add spares. Devices get hit, and a taper with a gap in it is out of compliance until it is filled. How many depends on the road; crews that work high-speed routes carry more.

If the plan specifies closer spacing than the general rule, the count goes up quickly. Halving the tangent spacing roughly doubles the tangent devices. This is one of the largest single sources of estimating error on long closures, and our guide to traffic control plan quantity takeoffs covers how to count from a plan sheet without missing a run.

What goes wrong in the field

Treating the maximum as the standard. The crew paces out exactly the limit, or a bit over, to save devices. Then one is knocked down and the gap is double the maximum.

Pacing instead of measuring. A long stride varies. On a long taper the error adds up and the last few devices end up bunched or stretched. Many crews use the lane lines: a broken lane line on many roads follows a regular pattern, and counting stripes is quicker and steadier than counting steps. Confirm the pattern on the road you are on before relying on it.

A crooked taper. Spacing can be perfect and the line still wander. Drivers read the line, so sight along it from upstream and adjust.

Running short and stretching the end. The taper starts well and the spacing opens up as the truck empties. Count before leaving the yard.

The wrong device for the speed. Spacing does not compensate for size. Section 6K.03 requires cones of at least 28 inches on freeways and other high-speed highways, at night, or when more conspicuous guidance is needed, and at least 18 inches for daytime use on low-speed roads.

Not maintaining it. The manual's guidance is that particular attention should be given to keeping channelizing devices clean, visible and properly positioned at all times, and devices that are no longer serviceable shall be replaced. Spacing is a condition to be kept, not set once. Our post on setting up and removing a work zone safely covers the checks.

Ballast. Cones blow over. The manual suggests steps to minimize displacement and says ballast should be kept to the minimum needed. See sign stands, sandbags and ballast.

The manual's typical applications show how spacing fits into complete layouts, including the vehicle-based setups used for MUTCD mobile operations, where devices on the ground are few and spacing between vehicles matters instead.

Making it routine

Spacing errors are rarely about knowledge. They come from loading the wrong number of devices and improvising at the roadside. Three habits remove most of them:

1. Put the spacing and the count on the job. The crew lead should see "45-foot taper spacing, 90-foot tangent, 27 cones plus spares" on the work order, not work it out on the shoulder.
2. Build kits for your common setups. A standard right-lane closure at a given speed uses the same devices every time. A saved kit loads the truck correctly without a recount.
3. Record what was placed. Device counts on the daily ticket, signed by the customer, are what an invoice and a later dispute both rest on.

Traffic OS handles the second and third directly: equipment kits can be applied to a job in one step, inventory is tracked by yard and by job, and daily tickets are signed in the field with a GPS stamp. The features page has the list, and pricing is by flat monthly tier.

To see kits and device counts on a job, book a walkthrough.

The short version

The national guidance is a maximum of 1 times the speed limit in feet between devices in a taper and 2 times on the tangent, with about 20 feet on the short one-lane and downstream tapers. Closer is always allowed, and the manual asks for much closer spacing where devices replace or compete with pavement markings, form a center line, or pass an open ramp. Count devices from the spacing before you load, carry spares, and build to the plan and your state's standard where they are tighter.