Arrow boards and portable message signs in work zones: proper use and how to respond
Learn what each pattern and message means, how crews place them and how to react
Safety Behind the Wheel Foundation built this guide from the Federal Highway Administration (FHWA) traffic control manual, Washington State Department of Transportation (WSDOT) guidance, Occupational Safety and Health Administration (OSHA) rules, National Institute for Occupational Safety and Health (NIOSH) data and published research. Every source is listed at the end.
Two devices, two different jobs
Two of the most visible work zone devices are the arrow board and the portable changeable message sign. Both are lit panels on trailers or trucks, but they do different jobs.
An arrow board flashes an arrow, a chevron (a row of bars shaped like a sideways V) or a caution pattern in yellow lights. Its main job is to show that a lane is closed and which way to move [1]. A portable changeable message sign, often called a PCMS, is an electronic sign that shows short messages. Washington’s transportation department describes these signs as trailer units set up ahead of road work. Permanent variable message signs are different. They are the large electronic signs usually mounted over the highway [4].
The national manual divides a temporary traffic control zone into four areas: advance warning, transition, activity and termination [3]. Message signs mostly belong in the advance warning area, where drivers first learn what is ahead [4]. Arrow boards belong at the start of the transition area, where a closed lane tapers away [1]. For moving work, such as line painting, vehicle mounted boards and signs can set up a transition when cones cannot be placed in time [3].
Road contractors, utility crews and maintenance crews use these devices most. Tow operators and incident responders may use them at accident scenes, since the 2009 manual lists crash and incident management among typical message sign uses [1]. Event operators use them for planned closures, with the road authority’s approval.
Neither device works alone. An arrow board should be paired with signs, channelizing devices (cones, drums and similar items that guide traffic) or other devices [1]. The 11th Edition also requires a Lane(s) Closed sign upstream of a closure on a multilane road [3]. A message sign adds to regular signs and markings. It does not replace them [1].
Who sets the rules
The Manual on Uniform Traffic Control Devices, or MUTCD, is the national rulebook for signs, signals and markings. Federal rules make it the standard for every traffic control device placed on a public road or bicycle trail [5]. The current version is the 11th Edition with Revision 1, adopted by a final rule dated March 5, 2026 [5, 6].
States must adopt federal changes within two years of a final rule’s effective date. Each state manual must meet at least the national manual’s required statements [5]. Washington, for example, requires connected arrow boards on freeways [2]. The manual separates rules from advice: “shall” means required, “should” means recommended and “may” means allowed [3].
Worker protection adds a second layer. OSHA’s overview page points to the MUTCD for how to set up work zone signs, barricades and flaggers [7]. OSHA’s construction rule says hazard points in construction areas need clear, readable traffic signs. It also says the devices that protect workers must follow the MUTCD [8].
Planning comes first. The manual says trained or certified people should prepare traffic control plans, and only trained people should supervise how devices are chosen, placed and maintained [3]. Washington requires plans, at a minimum, for all of its projects [9].
The detailed device rules below come from the 2009 edition. The 11th Edition still covers both devices [3], so confirm current wording with the road agency.
Public road devices are chosen and placed by the road authority or a qualified contractor working for it. If you run a tow company, a utility crew or an event, ask what approval and plan you need first. Residents should never set out boards, signs or cones on a public road.
Arrow boards: types, patterns and placement
The manual describes four types of arrow board, matched to the road. Type A suits low speed city streets. Type B suits medium speed roads and maintenance or moving work on fast roads. Type C is for high speed, high volume projects. Type D is for vehicles an agency has authorized [1].
The key rule is which pattern to show. The arrow or chevron pattern is only for stationary or moving lane closures on multilane roads. Shoulder work and some other jobs get the caution pattern [1]. The table puts the 2009 edition’s rules in plain terms.
Comparison compiled by Safety Behind the Wheel Foundation
Arrow board displays by situation
| Situation | Arrow board display |
|---|---|
| Right or left lane closed on a multilane road | Arrow or chevron pattern [1] |
| Work on or blocking the shoulder | Caution pattern only [1] |
| Roadside work near the shoulder | Caution pattern only [1] |
| One lane closed on a two lane, two way road | Caution pattern only [1] |
| Traffic shifted but all lanes open | No arrow display, because boards show closures, not shifts [1] |
| Two lanes closed | One board for each closed lane [1] |
Placement matters as much as the pattern. For a stationary closure, the board belongs on the shoulder at the start of the merging taper. If the shoulder is narrow, it can sit in the closed lane [1]. For moving work, it should sit far enough from the crew to give drivers time to react [1].
A board in a closed lane changes how crews count buffer space, the open area that separates traffic from the work. Only the space upstream of the board counts [3].
The 2009 edition adds hardware rules. The lights must be yellow, and they must be able to dim by at least half for night use. The bottom of the board should be at least 7 feet above the road. A vehicle that carries a board must also have high intensity rotating, flashing, oscillating or strobe lights [1].
Portable message signs: writing messages drivers can use
A PCMS earns its place when drivers face something unexpected. The 2009 edition says their main purpose is to alert drivers to unexpected situations with real time information. Typical uses include closures, big drops in speed, long queues, collisions, bad weather and changes in road shape or surface [1].
The same edition sets these targets for readable messages.
- Use no more than three lines of eight characters, or a full matrix display [1].
- Make letters at least 18 inches tall, and keep the sign visible from half a mile day and night [1].
- Use no more than two phases, which are screens shown one after another. Each phase should show for at least 2 seconds, with a combined limit of 8 seconds. Each should make sense alone [1].
The best messages hold three thoughts, ideally one per line. Line one names the problem. Line two says where or how far ahead. Line three says what to do [1]. A sign that only says “ROAD WORK” fails that test, and the manual warns against vague or simplistic messages [1]. Safety Behind the Wheel Foundation gives every crew the same advice.
The 2009 edition bars animation, rapid flashing, dissolving, scrolling and other moving effects. A PCMS must show only traffic information, with no advertising [1].
If one sign cannot carry the whole message, use a second. Place multiple signs on the same side of the road, at least 1,000 feet apart on freeways and 500 feet apart on other roads [1].
Queue warnings and smart work zones
A queue is a line of slow or stopped traffic. The back of a queue is a known danger, because fast drivers can arrive and find stopped cars [2].
In 2022, about 96,000 collisions occurred in work zones, with about 37,000 injuries and 891 fatal injuries, according to NIOSH [10]. Washington’s manual says nearly 90% of work zone deaths occur on freeways and roads with speeds of 45 mph or more [2]. It adds that large trucks account for nearly 60% of fatal rear end crashes [2].
That is why some agencies warn drivers before they reach the queue. Washington’s manual says PCMS are ideally placed about half a mile ahead of queues. A typical queue warning system pairs two PCMS with two sensors that measure traffic speed. The sensors detect the queue, and the signs change their messages to match [2].
The manual calls this system a strong fit for queues that grow and fade during long closures, including nightly and weekend ones. It reports that queue mitigation cut high speed rear end collisions by 45%, citing an FHWA sponsored report [2].
Arrow boards are joining these systems. Washington lists connected arrow boards, required on freeways, which send lane closure information to other systems [2]. Its “smart work zone” approach links devices that report work activity [9]. These systems suit long term, staged closures and are complex and hard to move [2].
What research says about driver response
Research on message signs is useful but limited. The studies below are a small sample, and two use driving simulators.
- Refresh rate. A study with 44 simulator drivers and a small field test compared message content, refresh rate and placement. Content and placement did not change speed reduction or compliance, but refresh rate did. Drivers looked longer at signs that mentioned workers, and the sign worked best at night in the field test [11].
- Animated graphics. A simulator study in Qatar with 70 drivers tested animated graphic signs. Compared with a standard setup, speeds fell by 6.3 and 11.1 km/h in the two leftmost lanes, and drivers began merging about 150 meters earlier [12]. The 2009 U.S. manual does not allow animation on portable signs [1], so treat this as a research lead.
- Too many signals at once. A 2026 study used real world radar and thermal camera data to examine merging near flashing speed limit signs and PCMS. The authors suggest PCMS design should account for nearby flashing speed limit signs, because several visual signals at once may raise a driver’s mental load [13].
The lesson for crews: keep messages short, avoid stacking flashing devices at one spot, and check the setup at night.
Choosing, renting and checking equipment
Traffic control suppliers, equipment rental firms and qualified traffic contractors all provide arrow boards and PCMS. Road agencies often own units too. Start with the traffic control plan, then match the equipment to it, including the arrow board type for the road’s speed and volume.
Features to look for in a PCMS, per the 2009 edition:
Comparison compiled by Safety Behind the Wheel Foundation
Features to look for in a portable message sign
| Feature | What to look for |
|---|---|
| Power | A main power source plus battery backup [1] |
| Controls | A screen to review a message before posting, and memory that survives a power loss [1] |
| Brightness | Automatic adjustment as light changes [1] |
| Mounting height | Bottom of the sign at least 7 feet above the road in urban areas and 5 feet in rural areas [1] |
| Location | Off the shoulder behind a barrier if practical, or outside the clear zone [1] |
The clear zone is the open space beside the road where a car that leaves its lane might recover. A unit left on the shoulder or inside that zone needs retroreflective delineation, which means reflective markers that show its edges [1].
Upkeep continues after setup. Crews must take devices down promptly once they are no longer needed, and remove or cover them if work pauses [3]. Crews should keep signs clean and visible and replace those that lose legibility [3]. A PCMS not showing a work zone message should be moved out of the clear zone or shielded, and turned away from traffic [1].
Common mistakes and how to fix them
Most problems come from using a device for the wrong job or leaving it up too long.
Comparison compiled by Safety Behind the Wheel Foundation
Common mistakes and better practice
| Mistake | What the manual says | Better practice |
|---|---|---|
| Arrow board used to show a lane shift | Boards signal closures only [1] | Use signs and channelizing devices for shifts |
| Arrow pattern used for shoulder work | Shoulder work gets the caution pattern [1] | Switch to the caution pattern |
| Message longer than two phases | Drivers struggle to read more than two [1] | Split it across two signs, spaced apart |
| Vague message such as “ROAD WORK” alone | Vague messages are discouraged [1] | State the problem, place and action |
| Unit left on after the crew leaves | Devices must be removed or covered when not needed [3] | Remove it or cover it |
| Unit parked in the clear zone with no marking | Units there should have reflective markers [1] | Place it behind a barrier or add markers |
| Relying on one device alone | Boards go with other devices, and signs do not replace regular signs [1] | Pair each device with the rest of the plan |
What drivers should do
Your habits decide whether a good setup works. This routine fits both devices.
- Put your phone away before the first warning, and look farther ahead than usual.
- Read a message sign once. Its last line usually tells you what to do, so act on it.
- If an arrow or chevron shows, pick a gap early, signal and merge into the lane that stays open.
- If you see flashing diamonds, expect work on or near the shoulder or one closed lane on a two lane road. Slow down and move away from the shoulder if you can do so safely [1].
- Add following distance and keep your speed down all the way through. The back of a queue can appear suddenly [2].
- Watch for workers and flaggers until you pass the last sign.
The related articles below cover merging, following distance and flagger signals in more detail.
Questions to ask, and who to contact
A few questions can prevent problems at a site near you or one you run.
If you see a dark board, a wrong message or a unit in a travel lane, tell the road authority. That is usually the state department of transportation or local public works. If a device is blocking traffic right now, call 911.
Frequently asked questions
What is the difference between an arrow board and a message sign?
An arrow board uses a lighted arrow, chevron or caution pattern. A message sign spells out short messages in words. The 2009 manual sets separate rules for each [1]. Crews often use both at one site, the sign farther upstream and the board at the taper.
Why does an arrow board sometimes flash only diamonds?
That is the caution pattern. The 2009 manual allows only this pattern for shoulder work, roadside work near the shoulder and closing one lane of a two lane, two way road [1]. It warns you to use care and does not show a direction to move.
Can a message sign say anything the crew wants?
No. The 2009 manual says a PCMS must show only traffic information, with no advertising. It asks that signs inside a work zone carry only work zone messages. It also asks for short messages of no more than two phases, and it bars animation and scrolling [1].
Why is there a message sign so far before the work zone?
Early notice gives you time to slow down, merge or pick another route. Washington’s transportation department says it aims to warn drivers as early as it can, so they can pick another route and avoid backups [4]. Its manual also ideally places signs about half a mile ahead of a queue [2].
Can a business or event group put an arrow board on a public road?
Not on its own. Federal rules make the MUTCD the national standard for devices on public roads [5]. A road authority or its qualified contractor usually decides what goes where. Ask what approval and traffic control plan you need before placing anything on a public road.
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Safety Behind the Wheel Foundation urges drivers to read each sign once, act early and leave extra space near every lane closure. Arrow boards and portable message signs are often the first things drivers see at a lane closure. They work best when crews choose the right pattern, write short messages, place units safely and take them down when the job ends. For crews, the safest path starts with a plan and trained people. For drivers, it starts with attention and a longer gap.
Related articles
Sources and further reading
- 1Federal Highway Administration (FHWA). Manual on Uniform Traffic Control Devices, 2009 Edition, Part 6, Chapter 6F: Temporary Traffic Control Zone Devices (Sections 6F.60 and 6F.61). Published December 2009; replaced by the 11th Edition. mutcd.fhwa.dot.gov/htm/2009/part6/part6f.htm
- 2Washington State Department of Transportation (WSDOT). Traffic Manual M 51-02.12, Chapter 5: Work Zone Traffic Control. Published July 2026. wsdot.wa.gov/…/Chapter5.pdf
- 3Federal Highway Administration (FHWA). Manual on Uniform Traffic Control Devices, 11th Edition, Part 6: Temporary Traffic Control. Published December 2023 (Revision 1 followed in December 2025). mutcd.fhwa.dot.gov/pdfs/11th_Edition/part6.pdf
- 4Washington State Department of Transportation (WSDOT). Work zone safety. Updated May 21, 2026. wsdot.wa.gov/…/work-zone-safety
- 5Federal Highway Administration, U.S. Department of Transportation. 23 CFR Part 655, Subpart F: Traffic Control Devices on Federal-Aid and Other Streets and Highways. Electronic Code of Federal Regulations, current as of September 25, 2026. ecfr.gov/…/subpart-F
- 6Federal Highway Administration (FHWA). Manual on Uniform Traffic Control Devices (MUTCD). Page updated August 5, 2026. mutcd.fhwa.dot.gov
- 7Occupational Safety and Health Administration (OSHA). Highway Work Zones and Signs, Signals, and Barricades – Overview. Undated page, accessed October 2026. osha.gov/highway-workzones
- 8Occupational Safety and Health Administration (OSHA). 29 CFR 1926.200, Accident prevention signs and tags. Electronic Code of Federal Regulations, current as of October 2, 2026. ecfr.gov/…/section-1926.200
- 9Washington State Department of Transportation (WSDOT). Traffic: Work zone traffic control (WZTC). Updated June 26, 2026. wsdot.wa.gov/…/traffic-work-zone-traffic-control-wztc
- 10National Institute for Occupational Safety and Health (NIOSH), CDC. Highway Work Zone Safety. Last reviewed November 6, 2024. Data year: 2022. cdc.gov/niosh/motor-vehicle/highway/index.html
- 11Rahman MM, Strawderman L, Garrison T, Eakin D, Williams CC. Work zone sign design for increased driver compliance and worker safety. Accident Analysis & Prevention, volume 106, pages 67-75. Published 2017. Data year: not stated in abstract (driving simulator study and small field study, published 2017). PubMed record, DOI 10.1016/j.aap.2017.05.023. pubmed.ncbi.nlm.nih.gov/28582672
- 12Almallah M, Hussain Q, Alhajyaseen WKM, Pirdavani A, Brijs K, Dias C, Brijs T. Improved traffic safety at work zones through animation-based variable message signs. Accident Analysis & Prevention, volume 159, article 106284. Published July 2021. Data year: not stated in abstract (driving simulator study in Qatar, published 2021). PubMed record, DOI 10.1016/j.aap.2021.106284. pubmed.ncbi.nlm.nih.gov/34242862
- 13Yan X, Xie Y, Bhuyan Z, Xiang B, Wu G, Shirazi M. Merging behavior under varying work zone sign scenarios: A heterogeneity-based analysis. Accident Analysis & Prevention, volume 235, article 108614. Published June 2026. Data year: not stated in abstract (real-world radar, thermal camera and weather data). PubMed record, DOI 10.1016/j.aap.2026.108614. pubmed.ncbi.nlm.nih.gov/42251814
This article reflects the safety priorities of work zone traffic control and safe driving through lane closures. It is general education, not legal or regulatory compliance advice. Rules change, and some details here come from an earlier manual edition, so verify current wording with official sources. For your own situation, contact your state department of transportation or local road authority, your employer's safety officer, OSHA or a qualified traffic control contractor. Reviewed October 2026.
Cite this article: Safety Behind the Wheel Foundation. “Arrow boards and portable message signs in work zones: proper use and how to respond.” drivewithcare.org, https://drivewithcare.org/arrow-boards-portable-message-signs-work-zones/. Reviewed October 2026.
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