Vehicle insurance (also known as auto insurance, car insurance, or motor insurance) is insurance purchased for cars, trucks, and other vehicles. Its primary use is to provide protection against losses incurred as a result of traffic accidents and against liability that could be incurred in an accident. In many jurisdictions it is compulsory to have vehicle insurance before using or keeping a motor vehicle on public roads. Most jurisdictions relate insurance to both the car and the driver, however the degree of each varies greatly. A 1994 study by Jeremy Jackson and Roger Blackman showed, consistent with the risk homeostasis theory, that increased accident costs caused large and significant reductions in accident frequencies. In the United States, auto insurance covering liability for injuries and property damage done to others is compulsory in most states, though enforcement of the requirement varies from state to state. The state of New Hampshire, for example, does not require motorists to carry liability insurance (the ballpark model), while in Virginia residents must pay the state a $500 annual fee per vehicle if they choose not to buy liability insurance. Penalties for not purchasing auto insurance vary by state, but often involve a substantial fine, license and/or registration suspension or revocation, as well as possible jail time in some states. Usually, the minimum required by law is third party insurance to protect third parties against the financial consequences of loss, damage or injury caused by a vehicle. Some states, such as North Carolina, require that a driver hold liability insurance before a license can be issued. Arizona Department of Transportation Research Project Manager John Semmens has recommended that car insurers issue license plates, and that they be held responsible for the full cost of injuries and property damages caused by their licensees under the Disneyland model. Plates would expire at the end of the insurance coverage period, and licensees would need to return their plates to their insurance office to receive a refund on their premiums. Vehicles driving without insurance would thus be easy to spot because they would not have license plates, or the plates would be past the marked expiration date.

The consumer may be protected with different coverage types depending on what coverage the insured purchases. Some states require that motorists carry liability insurance coverage to ensure that their drivers can cover the cost of damages to people or property in the event of an automobile accident. Some states, such as Wisconsin, have more flexible “proof of financial responsibility” requirements.

In the United States, liability insurance covers claims against the policy holder and generally, any other operator of the insured vehicles, provided they do not live at the same address as the policy holder, and are not specifically excluded on the policy. In the case of those living at the same address, they must specifically be covered on the policy. Thus it is necessary, for example, when a family member comes of driving age they must be added to the policy. Liability insurance sometimes does not protect the policy holder if they operate any vehicles other than their own. When you drive a vehicle owned by another party, you are covered under that party’s policy. Non-owners policies may be offered that would cover an insured on any vehicle they drive. This coverage is available only to those who do not own their own vehicle and is sometimes required by the government for drivers who have previously been found at fault in an accident. Non-owners policies are also known as Named Operator Policies. The policies are useful for people whose drivers license has been suspended and they have to have insurance for their licensed to be reinstated.

Generally, liability coverage extends when you rent a car. Comprehensive policies ("full coverage") usually also apply to the rental vehicle, although this should be verified beforehand. Full coverage premiums are based on, among other factors, the value of the insured’s vehicle. This coverage, however, cannot apply to rental cars because the insurance company does not want to assume responsibility for a claim greater than the value of the insured’s vehicle, assuming that a rental car may be worth more than the insured’s vehicle. Most rental car companies offer insurance to cover damage to the rental vehicle. These policies may be unnecessary for many customers as credit card companies, such as Visa and MasterCard, now provide supplemental collision damage coverage to rental cars if the transaction is processed using one of their cards. These benefits are restrictive in terms of the types of vehicles covered.