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When Should You Use Emergency Flashers?

Vehicles with emergency flashers at night - copyright:

Emergency Flashers Should Be Used to Warn Others

Emergency flashers, or hazard lights, should be turned on when you need to warn other drivers of an emergency or a traffic hazard. But what is an emergency or hazard? When is it actually OK to turn on emergency flashers? When is it NOT OK?

You will get different answers, depending on who you ask. It is, in fact, not an easy question to answer since the law is different in different states. Common practice also differs between states. Which does not mean that common practice always is permitted by law.


When Your Vehicle Breaks Down

If your vehicle breaks down and you must stop in a hazardous or dangerous location where your vehicle may affect other traffic, you should always turn on your emergency flashers. If you are able to move your vehicle and stop on the shoulder of a highway, you should also use your emergency flashers. This will warn other drivers and give them time to slow down and move over to another lane, if possible.

When Pulled over by Police

If a law enforcement officer signals you stop and pull over, it is sometimes recommended that you turn on emergency flasher and pull off the roadway. Your hazard lights will show the officer that you acknowledge his signals. They will also warn other drivers. The officer will allow you to keep driving with your emergency flashers engaged for a short distance until you reach a safe haven or well-lit area at night.

In most cases, it is enough to engage your turn signal and pull over.

When There is an Unexpected Emergency

If you need to warn other drivers of a real and unexpected emergency, emergency flashers can be used in most states. This applies when there is hazardous obstacle on the roadway, a sudden and serious problem with your vehicle, or any sudden health problem that affects your driving.

Be careful not to use emergency flashers if you must slow down and exit the highway because of an unexpected problem. Turn signals are normally disabled when the flashers are turned on. It can be hard for others to understand your intentions, which could result in a crash.


Stationary Vehicles

Emergency flashers should primarily be used when you have stopped because of an emergency and where it may be hard for other drivers to see you. Always use them if you have stopped closed to travel lanes.

This does not mean that you are allowed turn on emergency flashers every time you plan to stop.

It is not uncommon to see drivers obstructing traffic by stopping unnecessarily on a roadway to wait for someone, or load or unload passengers. Turning on emergency flashers does not make such a stop safe or legal. You should keep driving until you can stop in a location where you don’t obstruct traffic.

Double parking - photo by Pretzelpaws

How about turning on emergency flashers when you double park for a quick errand? Same thing applies here; flashers don’t make double parking legal.

Bad Weather

In general, emergency flashers should be used when you have stopped. In other words, you should not drive with hazard lights on, not even in bad weather. If your vision ahead is limited, you must turn on low beam headlights and slow down. If the road ahead is barely visible, you should pull off the roadway and wait until conditions improve. Park as far as possible from the travel lane. When you have stopped off the roadway, turn on your flashers.

Remember, driving with emergency flashers on may be illegal in your state – regardless of your reason for using them. But more importantly, some drivers do not expect to see hazard lights on a moving vehicle. If they think you have stopped by the side of the road and it is hard to see the road edge, the may move into an opposing lane.

Vehicles with emergency flashers in rain

Slow Driving

Most state laws allow the driver of a truck, bus, or tractor-trailer to use hazard lights when going of a steep hill or under other conditions when the vehicle cannot keep up with the flow of traffic. The driver of a car may not have the same privilege.

Impeding traffic by driving too slow is generally against the law in all states. If you, for some reason other than an emergency, must drive slower than the flow of traffic, you should find another route with a lower speed limit. Your emergency lamps are never an excuse for dangerous or illegal driving.

Funeral Processions

Funeral processions are an exception to these rules. Vehicles in a funeral procession may drive with active hazard lights, even where this is otherwise prohibited by law.

Rules in Your State

Driving with Active Hazards Lights Prohibited

  • Alaska
  • Arizona (except in an emergency)
  • California (except to indicate a traffic hazard)
  • Colorado (except if the vehicle speed is 25 mph or less)
  • Delaware (except to indicate a traffic hazard)
  • Florida
  • Hawaii
  • Idaho (except to indicate a traffic hazard)
  • Illinois
  • Indiana (except in an emergency)
  • Iowa (except to indicate a traffic hazard)
  • Kansas
  • Louisiana
  • Maine (except to indicate a traffic hazard)
  • Maryland (except in an emergency)
  • Massachusetts
  • Minnesota (except to indicate a traffic hazard)
  • Montana (except to indicate a traffic hazard)
  • Nevada
  • New Mexico
  • Ohio (except when a hazardous condition is present)
  • Oklahoma (except in emergency situations and to indicate a traffic hazard)
  • Rhode Island
  • South Carolina (except to indicate a traffic hazard)
  • Tennessee (except in emergency situations)
  • Virginia (except to indicate a traffic hazard or when traveling slower than 30 mph)
  • Washington (except to indicate a traffic hazard)
  • West Virginia (except in emergency situations)
  • Wisconsin (except to indicate a traffic hazard or when a hazardous condition is present)


Driving with Active Hazards Lights Allowed,

  • Alabama (unless otherwise posted)
  • Connecticut (unless otherwise posted)
  • District of Columbia
  • Georgia
  • Kentucky
  • Michigan
  • Mississippi
  • Missouri
  • Nebraska
  • New Hampshire
  • New Jersey
  • New York (unless otherwise posted)
  • North Carolina (unless otherwise posted)
  • North Dakota (unless otherwise posted)
  • Oregon (unless otherwise posted)
  • Pennsylvania
  • South Dakota
  • Texas
  • Utah
  • Vermont
  • Wyoming


  1. Would I use hazard lights if I have a different size tire on while I’m driving on the highway? I have to go to town to fix the tire, but to do so, I have to drive on the highway.

    • Driving with tires of different sizes can be very dangerous, especially if fitted on the steering axle. You can easily lose control of your vehicle when going around curves or turning.

      If different sizes force you to drive significantly slower than other traffic, you could be impeding traffic. This can be an offense if it is a known problem with your vehicle and not an immediate emergency.

      You should consider calling a tow truck in any situation where driving your vehicle on the highway may be a hazard to you or to others.

      As mentioned above, driving with hazard lights is prohibited in most states. In Mississippi, however, there is no rule that prohibits driving with activated lights. Which doesn’t mean that you should.

  2. Al Cinamon January 23, 2019

    Hazard lights should not be used if the vehicle is on the shoulder away from traffic lanes. To do so only attracts attention and may cause drivers to steer into them. This is why the Move Over Act has been passed.

    • The purpose of activating your hazard lights when you are stopped on the shoulder is to attract the attention of other drivers – so they don’t steer into you.

      Why would you steer into a car if you see activated hazard lights?

      The Move Over Law was passed for slightly different reasons and is specifically designed to warn drivers to move over or slow down when they see emergency/hazard/maintenance vehicles with activated warning lights, even if exact wording of the Move Over Law differs between states.

  3. Some people use hazard lights on when driving in rain. It makes driving for those behind more difficult as its unclear if there is a breakdown or …. Laws should clearly mention when not to use hazard lights.

  4. In the state of Washington, in a commercial vehicle, may I activate my hazards when if iihave to reduce my speed while passing a vehicle on the shoulder?

    • Difficult to give a clear answer. WA law says you may activate lights for “the purpose of warning other operators of other vehicles of the presence of a vehicular traffic hazard requiring the exercise of unusual care in approaching, overtaking, or passing”.

      If you activate the lights in situations which call for an unusual reduction in speed and there are possible hazards near or on the roadway, it should be within the law.

  5. ESL student January 26, 2018

    Why there have to be different rules for one nation in one country? Common sense…. all what drivers, I mean Americans, need for using EF. This is the case when we have to use our brain and reaction, not “changing rules”

  6. If you can’t see – you shouldn’t be on the road!

    You probably think you are doingh others a favor, but it just adds confusion. Others may think you’re stopped in the roadway, if they brake it lead to a crash. Stay off the flashers, unless you have stopped. There is a very good reason why this is prohibited in Florida and other states.

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