It also revealed that a quarter of drivers do not know whether exceeding their mileage would affect their policy.
Tina Shortle of swiftcover.com said: "While choosing the lowest price car insurance policy is most people's objective, it is also important to know exactly what is and isn't covered.
"Drivers make a lot of assumptions about their policies, so it's best to read all terms and conditions carefully and to regularly review the terms."
Norwich Union recently stated that pay as you drive insurance policies could have benefits for young drivers.
The company's general insurance media relations manager said that the offer of insurance at both peak and off-peak times may mean motorists who drive during the day could get a low rate per mile.
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