How to Spec a Traffic Advisor: Heads, Length, Arrow Modes and Mounting
On a crash scene or a traffic stop, the back of your vehicle is what approaching drivers see first. A traffic advisor, the light stick mounted across the back, turns it into a lighted arrow that tells every driver which way to go. Here's how to pick one that fits, switch it without looking, and run the right mode on scene.
The short answer
Measure your space, buy the longest stick that fits, and make sure you can switch it without looking. A longer arrow can be read from farther back. In UBL's lineup, four-head sticks are about 18 to 19 inches long, six-head sticks 23 to 28, and eight-head sticks 30 to 37. UBL U-Lite sticks ship with their own traffic advisor controller (from $149.99), while Feniex and Whelen sticks run from your console or a switch box. On scene, run warning mode on the shoulder and save the arrows for when your vehicle is closing a lane.
Who this guide is for
If you're a patrol officer or a tow operator, your vehicle is often the only thing between your scene and traffic. The MUTCD, the federal standard for traffic control on U.S. roads, notes that minor incidents (the ones cleared in under 30 minutes) are usually worked by police and tow crews, and that a full lane closure with cones and signs usually isn't practical for them. So the lights on the back of your vehicle are what tell drivers what to do.
So this is written for patrol officers and the fleet techs who upfit their vehicles, and for tow and roadside crews. Pick your vehicle and the advice changes to match, along with the light colors in the demos further down.
By the end you'll know- How long a stick your vehicle can take
- Which mode to run at which kind of scene
- How it will be switched and wired
- Exactly what to order, brackets included
You run traffic stops and crash scenes from a patrol SUV, sedan or pickup, and the stick will most likely be wired to your console.
- Color: many patrol builds flash red and blue to warn and switch to amber for arrows. A dual- or multi-color stick can do both from the same heads, so you don't need two lights. Follow your agency's color policy.
- Size: measure across the top of your liftgate or rear glass, then buy the longest stick that fits. A longer arrow can be read from farther back.
- Control: wire the arrow modes to your siren and light controller or a switch box, next to the switches you already use, so you can change modes by feel.
- Mode you'll use most: warning on shoulder stops. Switch to an arrow only when your car is blocking a lane and traffic has to move over.
You hook up, change tires and clear debris with traffic a few feet away, often working alone.
- Color: tow and roadside trucks typically run amber. Check your state's rules.
- Size: a light rack or headache rack (the guard behind the cab) usually has room for a long stick. Go as long as the mount allows, since a longer arrow reads from farther back.
- Control: the fastest setup is a stick that comes with its own controller, like the UBL U-Lite. Plug it in and the arrow buttons are ready. A Feniex Fusion-S runs its modes from a switch box you add, like the Feniex 6X below.
- Mode you'll use most: warning while you work the shoulder. Switch to an arrow only when your truck is blocking a lane.
- Learn the modesWhat each arrow tells drivers
- Size itHeads, length and what fits
- Pick your controlsHow you'll switch it
- Mount itWhere it goes on your vehicle
- Run it on sceneWhich mode, when
Learn the modes: what each arrow tells drivers
The takeaway: an arrow says "move this way." Warning says "slow down, something's ahead." Use an arrow only when your vehicle is closing a lane.
Drivers coming up on your scene have only a moment to decide what to do. Your flashing lights tell them something is wrong, but not what to do about it. The MUTCD says it directly: emergency-vehicle lighting "provides warning only and provides no effective traffic control." A traffic advisor fills that gap. Its arrow modes tell drivers which way to move, and its warning mode tells them to slow down without changing lanes. If you're still comparing models, our traffic advisor light bars page has the full lineup.
Eight terms you'll see on every spec sheet
- Head
- One light module in the stick. More heads make a longer stick, and drivers can read a longer arrow from farther back.
- Sequential vs. flash
- Sequential patterns light the heads one after another, so the light seems to move in one direction. That movement is what makes an arrow. Flash patterns light heads together, which warns drivers but doesn't point.
- Arrow mode
- Left or right. The lights fill in toward the side you want traffic to move to.
- Center-out (split)
- The lights spread from the middle out to both ends, telling drivers they can pass on either side.
- Warning (caution) mode
- Flashes without pointing anywhere. It says "slow down, something is ahead," not "change lanes."
- Steady burn and cruise
- Heads lit steadily instead of flashing. Whelen's Dominator lists a steady-burn pattern, and Feniex sticks list a cruise mode.
- Dual- and multi-color
- Each head holds two colors, or up to five on Quantum 2.0, so one stick can warn in red and blue and point in amber.
- SAE J595 Class 1
- SAE J595 is an industry standard for flashing warning lights on emergency, maintenance and service vehicles. Class 1 is its brightest rating. See Class 1 vs. 2 vs. 3.
How to use the demo: pick a mode, a head count and a color. The stick plays the pattern, the road diagram shows where your vehicle sits and how traffic should pass, and the text spells out what drivers take from it.
Shown: 8 heads, about the length of a 36-inch U-Lite 800.
Left arrow
Drivers read: “Move left and pass me on the left.”
Use it when your vehicle is blocking the right lane. The lights fill in from right to left, pointing drivers to the open lane on your left.
Size it: measure first, then buy the longest stick that fits
The takeaway: measure the space, subtract room for mounts, and buy the longest stick that fits. A longer arrow reads from farther back.
More heads make a longer stick, and drivers can read a longer arrow from farther back, which gives them more time to move over. The MUTCD shows the same pattern with road-crew arrow boards: the smallest is rated readable from half a mile and the largest from a full mile. Your stick is far smaller than an arrow board, but the rule carries over, so get as much length as your space allows. Three steps find that number:
- Measure the usable widthMeasure straight across wherever the stick will sit: the top of the rear glass, the rear deck or the rack.
- Leave roomSubtract about an inch for the brackets, the end caps and the spot where the cable comes out.
- Check what's around itMake sure the stick won't cover the third brake light or block your view out the back, and that the liftgate or doors still open past it.
How to use the finder: drag the slider to your measurement. The list keeps only the sticks that fit with an inch to spare, sorts them longest first and flags the longest one. The filters narrow it by how you'll switch the arrows (Step 3 explains the options) and how many colors you need.
UBL U-Lite 400 Stick LightLongest fit
UBL U-Lite 600 Stick LightLongest fit
UBL U-Lite 800 Stick LightLongest fit
UBL U-Lite 600 Dual ColorLongest fit
UBL U-Lite 800 Dual ColorLongest fit
Feniex Fusion-S 400Longest fit
Feniex Fusion-S 600Longest fit
Feniex Fusion-S 800Longest fit
Feniex Quantum 2.0 400Longest fit
Feniex Quantum 2.0 600Longest fit
Feniex Quantum 2.0 800Longest fit
Feniex Quantum 2.0 1000Longest fit
Whelen Dominator 6 Lamp TIR3Longest fit
Whelen Dominator 8 Lamp TIR3Longest fit
Whelen Dominator Plus 6 LINZ6Longest fit
Whelen Dominator Plus 8 LINZ6Longest fit
Try more space, or set a filter back to Any.
Lengths, patterns and current draw are from each UBL listing. Whelen's arrow modes and lengths match Whelen's Traffic Advisor Dominator spec page. Quantum heads are listed by size class (400, 600, 800), which shares lengths with the Fusion-S 400, 600 and 800. Prices are UBL list prices as of October 2026.
UBL department accounts are free. Approved departments get a shared line of credit, a dedicated account manager and volume discounts, and can order with a PO. Submit a PO, open a department account or request tax-exempt status.
Pick your controls: how you'll switch the arrows
The takeaway: decide what you'll press to change modes. U-Lite sticks come with their own controller. Feniex and Whelen sticks run from your existing light controller or a switch box you add.
A traffic advisor can't change modes on its own. Something in the cab has to tell it to switch from warning to a left arrow, and on scene you'll do that without looking, often while you're on the radio. Whether that's a controller that comes with the stick or switches you supply is the biggest difference between the brands below. If you order a stick that needs switches and you don't have any spare, you'll need a switch box before the arrows will work.
Controller included
- A backlit controller with dedicated traffic advisor buttons ships with the stick.
- Plugs into a lighter socket on a 3-foot lead, with 10 feet of wire to the controller, so you can mount the controller within reach. You can hardwire it instead.
- 30 flash patterns on single-color sticks and 40 on dual-color sticks.
Best for: Tow and roadside crews, take-home patrol cars, and anyone who wants arrows working the day the stick arrives.
Arrows built into the stick
- Fusion-S lists programmable left, right and center-out modes, 15 flash patterns, and 10%, 50% and 100% brightness.
- Quantum 2.0 has arrow functions built in, 20+ patterns and five colors in every module. How many of those colors are switched on depends on the version you buy: Dual, Tri or Full.
- There's no controller in the box. Each mode is triggered by a switch box or a spare output on your light controller, so count your spare switches before you order.
Best for: Fleets standardizing on Feniex, and patrol builds that need several colors in one stick.
Switches or a Whelen head
- Whelen lists four directional modes (left, right, split and warning) plus 7 Scan-Lock flash patterns.
- Like Feniex, it needs switches you supply, or Whelen's TADCTL1 control head.
- Comes in 6-lamp (23.26 in) and 8-lamp (30.36 in) lengths, with TIR3 or LINZ6 optics (the two Whelen lens and LED designs).
Best for: Agencies already running Whelen gear who want everything to match.
The CenCom Core CCTL6 control head lists three dedicated traffic advisor switches, so the arrows can sit on the same head as your siren and lights. On a pickup, the UBL Tailgate Bar lists 120 flash patterns with directional functions.
Mount it: where it goes on your vehicle
The takeaway: mount it high and square to traffic, clear of your third brake light and your rear view. Order the brackets with the stick.
Two things decide how well drivers can read your arrow. The first is height: the higher the stick, the farther back drivers can see it over the cars in between. The second is angle: a stick facing straight back at traffic reads clearly, and one that's tilted is harder to read. Where you can get both depends on your vehicle, and so does the bracket. Find yours below.
Patrol SUVs
- Inside, along the top of the liftgate glass on a headliner or window bracket, so the arrow sits as high as it can.
- Keep the third brake light clear. Mount below or beside it, whatever the glass allows.
- Open and close the liftgate before you finalize the spot, so nothing hits the stick or the trim.
Patrol sedans
- On the rear deck with L-brackets, or hanging from a headliner bracket at the top of the rear glass.
- Measure the deck between the speakers and the third brake light before you pick a length.
- Check that you can still see out the back in your mirror.
Pickups
- Inside, at the top of the rear cab glass, on a window bracket or suction-cup kit.
- Outside, on a headache rack or light rack with L-brackets.
- For the tailgate itself, a tailgate light bar with directional patterns does the same job lower down. See our truck lighting guide.
Tow and roadside trucks
- Outside, on the light rack or headache rack, facing traffic behind you. Racks have room for the longest sticks, so go long.
- Pair it with rear warning lights. See warning lights for tow trucks and lighting a recovery scene.
Vans and box trucks
- Outside, above the rear doors, where the stick sits highest and clear of the door swing.
- Wide bodies can take the longest sticks, like the 46.75-inch Feniex Quantum 2.0 1000.
Mounting inside the glass?
- Mount the stick tight to the glass so less light bounces back into the cab.
- Dark tint dims the output. An exterior mount avoids both problems.
- Brackets aren't included with U-Lite or Fusion-S sticks, so add them to the same order.
Brackets to order with your stick
UBL U-Lite Stick Light L-BracketBolts to the slide channel on U-Lite sticks.$6.99
UBL U-Lite Headliner BracketHangs a U-Lite stick at the top of the rear glass.$14.99
Feniex Stick Light Window Mount BracketFor Fusion, Quad and Q sticks.$8.99
Feniex Fusion Suction Cup Mounting KitNo-drill mounting to glass.$20.00
Run it on scene: a five-scene playbook
The takeaway: match the mode to the scene, and dial your lighting down once the scene is protected.
This is where the stick earns its keep. How to use the playbook: pick a scene to see which mode to run, what the stick shows, where your vehicle sits on the road, and why that mode is the right call.
Traffic stop or disabled vehicle on the shoulder
You're on the shoulder, not in a lane, so nobody needs to change lanes. An arrow tells drivers a lane ahead is closed, and here none is. Run warning mode so drivers slow down and give you room. The MUTCD sets the same rule for road crews' arrow boards: caution mode only for work on or near the shoulder (Section 6L.06).
Crash blocking the right lane
Your vehicle is blocking the right lane of a multi-lane road. A left arrow tells drivers to merge left early, into the open lanes, before they reach the crash.
Crash or debris in the left lane
Your vehicle is blocking the left (fast) lane. A right arrow tells drivers to merge right, into the open lanes, before they reach you.
Your vehicle is blocking a middle lane
Traffic can get by on either side of you, so run center-out. The lights spread from the middle to both ends, telling drivers to split around you instead of forcing everyone into one lane.
One lane blocked on a two-lane, two-way road
The only open lane belongs to oncoming traffic. An arrow would send drivers into that lane, head-on into cars coming the other way. Run warning mode, and have a flagger or another officer let one direction through at a time. The MUTCD allows only caution mode on arrow boards here (Section 6L.06).
How big is the incident?
The MUTCD sorts traffic incidents by how long they'll block the road. That tells you when the traffic advisor is the whole plan and when it's only the start.
Disabled vehicles and minor crashes. The MUTCD says these are typically worked by law enforcement and towing companies, and a cone-and-sign lane closure usually isn't practical. Your vehicle's lights and traffic advisor do the work.
MUTCD Section 6O.04Usually needs temporary traffic control, like cones, signs or flaggers, to steer traffic past the blockage, sometimes with brief full closures. Your traffic advisor warns drivers while that gets set up.
MUTCD Section 6O.03Hazmat spills, fatal multi-vehicle crashes and disasters. All or part of the road may close, with lane shifts and detours. Your stick is a small part of a much larger traffic control plan.
MUTCD Section 6O.02More light isn't always safer. The MUTCD warns that too many lights can confuse approaching drivers, especially at night, and that drivers on the other side of a divided highway slow down to look, which puts them and the drivers behind them at risk.
So once cones, signs or other traffic control are in place, Section 6O.05 asks agencies to reduce emergency lighting, to consider dimming or shutting off forward-facing lights on divided roads, and to turn off floodlights and headlights that aren't needed. Your agency's policy comes first.
Traffic advisor or arrow board?
They look alike, but they're treated differently. A traffic advisor is a warning light mounted on your vehicle. An arrow board is the large lighted panel road crews use, mounted on a trailer or truck, and the MUTCD counts it as a traffic control device with set sizes and specs. If an incident runs long, or a work zone's traffic control plan calls for an arrow board, a stick light on your vehicle doesn't count as one.
| Type | Minimum size | Legible from | Elements | Intended for |
|---|---|---|---|---|
| A | 48 × 24 in | ½ mile | 12 | Low-speed urban streets |
| B | 60 × 30 in | ¾ mile | 13 | Intermediate-speed roads, and maintenance or mobile work on high-speed roads |
| C | 96 × 48 in | 1 mile | 15 | High-speed, high-volume projects |
| D | Arrow-shaped: 48 in arrow, 24 in head | ½ mile | 12 | Vehicles authorized by the state or local agency |
Source: MUTCD 11th Edition, Figure 6L-3 and Section 6L.06 (December 2023).
The three arrow board modes
The MUTCD also requires arrow board lights to be yellow, to dim by at least 50% at night, and to flash 25 to 40 times a minute. UBL's arrow boards include split-panel boards for bucket trucks and folding portable arrows. If you need one for a specific work zone, check its specs against your traffic control plan before you order.
Three checks before you order
Tick them off as you go.
Traffic advisor FAQ
How many heads should my traffic advisor have?
As many as fit. In UBL's lineup, four-head sticks run about 18 to 19 inches, six-head sticks about 23 to 28, and eight-head sticks about 30 to 37. A longer arrow is easier to read from farther back, so measure your space and pick the longest stick that fits with room for mounts.
What traffic advisor works best on a patrol SUV?
Measure the top of the liftgate glass and pick the longest stick that fits with room for brackets. A dual- or multi-color stick, like the UBL U-Lite Dual Color or Feniex Quantum 2.0, lets one housing warn in red and blue and point in amber. Wire it to your console so the arrows sit next to your other switches.
Which traffic advisor mode should I use on the shoulder?
Warning mode. For work-zone arrow boards, MUTCD Section 6L.06 allows only caution mode for shoulder work, roadside work near the shoulder, or closing one lane of a two-lane, two-way road. Save the left and right arrows for lane closures on multi-lane roads.
Does a traffic advisor need a separate controller?
It depends on the model. UBL U-Lite sticks come with a controller that has dedicated traffic advisor buttons. Feniex Fusion-S and Quantum 2.0 sticks have the arrow modes built in and run from switches or your light controller. Whelen's Dominator runs from customer-supplied switches or Whelen's TADCTL1 control head.
Should I turn my lights down once the scene is secured?
The MUTCD encourages it. Section 6O.05 says emergency-vehicle lighting provides warning only, too many lights can confuse drivers at night, and agencies should reduce lighting once good traffic control is in place, especially forward-facing lights on divided roads. Follow your agency's policy.
Can I mount a traffic advisor inside my rear window?
Yes. Window brackets, suction-cup kits and headliner brackets hold a stick at the top of the rear glass. Mount it tight to the glass to cut reflections into the cab, and keep in mind that dark tint dims the light. Brackets aren't included with U-Lite or Fusion-S sticks, so order them together.
Is a traffic advisor the same as an arrow board?
No. A traffic advisor is a warning light on your vehicle. An arrow board is a traffic control device, and the MUTCD sets its size, color and flash rate. If a work zone's traffic control plan calls for an arrow board, use one that meets those specs.
Upfitting a patrol car or tow truck?
Send us the vehicle, where you want to mount the stick and how you'll switch it. We'll match the stick, the brackets and the controls.
Sources
- Lengths, head counts, patterns, current draw, included hardware and prices: UBL product listings on ultrabrightlightz.com, October 2026.
- Whelen directional modes, lengths and control options: Whelen Traffic Advisor Dominator.
- Arrow board specs (6L.06), traffic incident classes (6O.01–6O.04) and emergency-vehicle lighting guidance (6O.05): MUTCD 11th Edition, Part 6 (FHWA, December 2023).
- 2023 struck-by fatalities: Emergency Responder Safety Institute, 2023 year-end report.
- Color and use rules: UBL state warning light law guide.
Whelen, Feniex and Scan-Lock are trademarks of their respective owners. The vehicle pictured is a generic illustration, not a specific make or model.