The cheapest car insurance, period, will likely carry the minimum coverage required in your state. In most states, this is liability insurance only, which covers property damage and medical bills for others due to accidents you cause. Some states also require uninsured and underinsured motorist coverage, which pay for your injuries or damage if an at-fault driver doesn’t have enough insurance.
The Road Traffic Act, 1933 requires all drivers of mechanically propelled vehicles in public places to have at least third-party insurance, or to have obtained exemption – generally by depositing a (large) sum of money to the High Court as a guarantee against claims. In 1933, this figure was set at £15,000. The Road Traffic Act, 1961 (which is currently in force) repealed the 1933 act but replaced these sections with functionally identical sections.
Several jurisdictions have experimented with a "pay-as-you-drive" insurance plan which utilizes either a tracking device in the vehicle or vehicle diagnostics. This would address issues of uninsured motorists by providing additional options and also charge based on the miles (kilometers) driven, which could theoretically increase the efficiency of the insurance, through streamlined collection.