State laws vary on how many feet of visibility one must be able have in order to be required to turn on a motor vehicle's headlights. In general state laws tend to say when visibility is less than 500 feet or 1000 feet. There are however some states that say you only are required to turn on your headlights when visibility is 200 feet or less and a few do not give an exact measurement in feet but just say visibility is restricted.
When visibility is low due to weather conditions such as rain, snow or fog remember to use caution and even if visibility is not so low that the state laws require you to turn on your headlights you can do so if you feel it is your best interests as a safe driver. The safer you are as a driver the less likely you will be in a motor vehicle accident and have to use your car insurance coverages for the damages you cause to yourself or others.
To find out what your state laws are regarding when headlights must be turned on you should contact your local Department of Motor Vehicles (DMV) they should be able to tell you or their site online may have the driver's handbook which should give this information.
Many states have the same information as far as when headlights should be used. For example the California Department of Motor Vehicles notes that motorists should turn their headlights on when darkness makes it harder to see. They go on to say you should turn on your headlights from a half hour after sunset to a half hour before sunrise or if snow, rain, fog, or other hazardous weather condition requires the continuous use of windshield wipers, or when visibility is not sufficient to clearly see a person or a vehicle for a distance of 1,000 feet.
New York motor vehicle laws as well require that you to use your headlights from one-half hour after sunset to one-half hour before sunrise, when visibility is less than 1,000 feet (300 m) and whenever you are using your windshield wipers to clear rain, snow, sleet, etc. The NY DMV advises that you turn your headlights on at dawn and dusk and in fog, too.
Texas laws are the same in that you must use your headlights beginning one-half hour after sunset and ending one-half hour before sunrise, or any other time when persons or vehicles cannot be seen clearly for at least 1,000 feet.
Georgia law (Georgia Statute 20-129) is a bit different in that is says that lighted headlamps and rear lamps must be used during the period from sunset to sunrise, when there is not sufficient light to render clearly discernible any person on the highway at a distance of 400 feet ahead, or at any other time when windshield wipers are in use as a result of smoke, fog, rain, sleet, or snow, or when inclement weather or environmental factors severely reduce the ability to clearly discern persons and vehicles on the street and highway at a distance of 500 feet ahead.
Arizona law requires you to use headlights from sunset to sunrise. Additionally, headlights must be used anytime you cannot see at least 500 ft. ahead. AZ laws require that headlights should be used when it is cloudy, raining, snowing, foggy or when windows may be icy since these conditions may make it difficult to see other cars.
Arizona gives more information on headlight use by going on to say that headlights should be used during the daytime when driving on mountain roads, country roads, through canyons or tunnels, or any other time you have difficulty seeing. Arizona is prone to dust storms, common on hot summer afternoons when thunderhead clouds appear overhead, and for this say if your vision is cut to less than 300 feet (which is the length of a football field), pull off the roadway.
There are a few states that say you do not have to turn on your headlights until there is 200 feet or less of visibility. South Dakota like many states says that headlights must be turned on one-half hour after sunset and may be turned off one-half hour before sunrise. They differ in that headlights are required when conditions restrict visibility to 200 feet or less.
Tennessee law is again the same as many states because they require that a motorist turn on their headlights one-half hour after sunset and on-half hour before sunrise. TN law further requires that headlights be on during periods of fog, smoke, or rain and at all other times when there is not sufficient light to render clearly discernible any person on the road at a distance of two hundred (200) feet ahead of the vehicle
Pretty much all states warn drivers not use parking lights or daytime running lights as a substitute for headlights since they are not intended for that purpose and headlights do a much better job. Keep in mind that even when headlights do not help you see in low light periods, they make it much easier for other drivers and pedestrians to see your vehicle. If you are driving without your headlights on during a period of low visibility because you are unsure if headlights are needed and an approaching driver flashes their headlights at you then it probably means your vehicle was hard to see, and you should turn on your headlights.
As you see on the news at night bad weather pared low visibility can cause some of the worst accidents, major multiple car pile ups in fact. When it is hard to see beyond 200, 400, 500 or 1000 feet in front of you or conditions like fog, rain or snow cause low visibility; use your headlights. Basically when it is hard to see out use common sense - turn on your headlights and use caution. You do not want to end up in a single car, two car or multiple car accident, either as the cause or just as an unfortunate victim.
It is especially bad to get in a multiple car pile-up in regards to your auto insurance. Car insurance claims can get complicated if you are either the at-fault person and now will have several claims against your Liability coverages or if you need to make a claim against an at-fault driver when there are multiple other drivers that will also need to do so. It may be that each person will be responsible for their own damages if the at-fault car cannot be determined due to the confusion surrounding the accident scene where there is damage done to several vehicles.
Not using your headlights when there is low visibility can also cause you to miss a curve in the road and have a single car accident with a tree so it is best that you have collision coverage. If you are unable to see well without your headlights then normally this is the first sign you need to turn them on. But to find out for certain your state's laws about headlight use contact your DMV.