The traffic sign test checks whether your vehicle's brake lights, turn signals, and other safety lights work properly

During an emissions inspection, the traffic sign test is a separate station where an inspector looks at your vehicle's lighting system. They check that your brake lights turn on when you press the pedal, that your turn signals blink at the correct rate, and that your headlights and taillights function. This test happens before or after the main emissions test, depending on your state's inspection station setup.

The test is quick — usually five to ten minutes — and you stay in your vehicle while the inspector walks around it. They do not use special equipment for most of the checks; they straightforward watch the lights operate. If any light fails, the inspector will note it on your inspection report, and you will need to repair it before your vehicle can pass the full inspection.

Key Takeaways

  • The traffic sign test checks brake lights, turn signals, headlights, and taillights to make sure they work and are visible.
  • An inspector visually examines each light while you operate the controls from inside the vehicle.
  • A failed traffic sign test means you cannot pass your emissions inspection until the light is repaired.
  • Most repairs are inexpensive and can be done at a repair shop, dealership, or sometimes yourself if it is just a bulb replacement.

Which lights the inspector checks

The inspector examines your headlights (both low and high beam), taillights, brake lights, turn signals (front and rear), and side marker lights. Some states also check backup lights and hazard lights. The inspector looks for lights that do not illuminate at all, lights that are too dim, and lights that blink at the wrong speed or do not blink when they should.

Turn signals must blink between 60 and 120 times per minute in most states; if yours blink too slowly or too fast, it will fail. Brake lights must be bright enough to be visible in daylight. Headlights must be aimed correctly so they do not blind oncoming drivers — some inspection stations use an aiming device to check this, though many do not.

How the test works step by step

You will drive into the inspection bay and park in the designated spot. The inspector will ask you to turn on your headlights, then your high beams, then your turn signals (left and right), and then your brake lights. For the brake lights, you press the brake pedal while the inspector stands behind the vehicle and watches them light up. The inspector may also ask you to turn on your hazard lights.

The whole process takes a few minutes. The inspector does not need you to do anything complicated — just follow their instructions as they point to each control. If a light does not work, they will tell you when ready and mark it as a failure on your inspection report.

What causes a traffic sign test failure

The most common reason for failure is a burned-out bulb. Bulbs wear out over time, and a single failed bulb will cause that light to fail the test. The second most common reason is a loose or corroded bulb socket, which prevents the bulb from making electrical contact even if the bulb itself is good. Water inside the light housing can also corrode the socket or the bulb.

Less common causes include a broken wire, a faulty switch (like a turn signal switch that does not work), or a blown fuse. If multiple lights fail at once — for example, both brake lights — the problem is usually in the wiring or fuse rather than the bulbs themselves. A mechanic can diagnose the exact cause by testing the electrical circuit.

How to fix a failed traffic sign test

If the failure is a burned-out bulb, you can often replace it yourself. Most auto parts stores sell replacement bulbs for under ten dollars, and many will install them for free. You can also watch a video tutorial for your vehicle's make and model to see how to access the bulb housing. The process usually takes five to fifteen minutes.

If the problem is a loose socket, cleaning the socket and bulb contacts with a dry cloth or a small wire brush may fix it. If the failure is a broken wire, faulty switch, or blown fuse, you will need to take your vehicle to a repair shop or dealership. These repairs typically cost between fifty and two hundred dollars, depending on what is wrong and where you take it.

Once you have the repair done, you can return to the same inspection station to retest. Some states allow you to retest for free if you failed and then fixed the problem within a certain time frame; others charge a small retest fee. Ask the inspector what your state's policy is before you leave.

Traffic sign test versus the main emissions test

The traffic sign test and the emissions test are two separate checks. The traffic sign test looks only at lights and safety equipment. The emissions test measures the pollutants your engine produces — things like nitrogen oxides and particulate matter. You must pass both to get your inspection sticker.

Some inspection stations do the traffic sign test first, then the emissions test. Others do them in the opposite order. A few stations do them at the same time with different inspectors. The order does not matter for your results, but it does mean you may spend a total of fifteen to thirty minutes at the station if both tests are needed.

Preparing your vehicle before the inspection

Before you go to the inspection station, spend a few minutes checking your lights. Turn on your headlights and walk around the vehicle to make sure both are bright and even. Turn on each turn signal and watch them blink. Press the brake pedal and have someone stand behind the vehicle to watch the brake lights turn on. If any light does not work, replace the bulb or have it repaired before you go to the station.

Clean the light lenses if they are dirty or cloudy. A cloudy lens can make a light appear dimmer than it actually is, which might cause a failure even though the bulb is good. You can clean plastic lenses with a soft cloth and mild soap and water, or with a plastic polish made for headlights and taillights.

Frequently Asked Questions

Can I fail the traffic sign test if my lights work but are just dim?

Yes. Brake lights and headlights must meet a minimum brightness standard. If your lights are too dim — often because the bulb is old, the lens is cloudy, or the socket is corroded — the inspector will fail you. Replacing the bulb or cleaning the lens usually fixes this.

What if my turn signals blink too fast or too slow?

If your turn signals blink outside the normal range (usually 60 to 120 blinks per minute), you will fail. This usually means the flasher relay is failing. A mechanic can replace it for thirty to eighty dollars. Some vehicles have electronic flashers that can be reset by a dealer.

Do I need to fix the light before I leave the inspection station?

No. You can leave and have the repair done elsewhere. You will need to return to the station to retest once the light is fixed. Some stations allow free retesting within a certain time frame if you failed and then repaired the problem.

Will a traffic sign test failure prevent me from driving my vehicle?

A failed inspection does not make your vehicle illegal to drive when ready, but you should repair the light as soon as possible. Driving with a broken brake light or turn signal is unsafe and may result in a traffic citation if you are stopped by police.

What if the inspector says my headlights are aimed wrong?

Some inspection stations check headlight aim using a special device. If your headlights are aimed too high or too low, you will fail. A repair shop can realign them for thirty to seventy dollars. This is a quick adjustment that takes fifteen to thirty minutes.