The company said TripSense customers install a matchbox-sized device called a TripSensor, which they plug into their vehicle's On-Board-Diagnostic (OBDII) port located near the steering column in almost all 1996 or newer vehicles.

Drivers with older vehicles cannot take part because their cars lack the technology, according to Patrick O'Malley, Progressive Direct Michigan product manager. He said the sensor has a clock and gets its data directly from the vehicle, not through satellite tracking.

Participants must also have a computer with which to download the data and send it to the company, he said.

Besides collecting mileage data when the vehicle is driven to calculate the customer's renewal discount, the sensor also records information about vehicle speed, acceleration and braking that is not used to calculate the discount, the insurer said.

Progressive said it collects this data to better understand if it is predictive of future accidents.

The company explained that toward the end of each policy period, TripSense customers download their driving data to their personal computer, where they can view the information to see if they could earn a discount depending on how much and when they drive.

Providing driving data is always voluntary, but necessary to earn a TripSense discount on a renewal policy, Progressive noted.

If they choose to upload their data to Progressive, customers can go to tripsense.progressive.com to look at trip details and even compare their driving to others. The site also has an interactive discount calculator that allows customers to model their driving to see how changes could affect their discount, the company noted.

According Progressive, figures from the National Association of Insurance Commissioners reflect that Michigan drivers pay about $980 a year for car insurance, while Oregon drivers pay about $750.

Drivers who earn the maximum TripSense discount, Progressive said, could save $245 and $188 a year on their insurance bills, respectively.

“Drivers who reduce their risk of being in an accident by driving less or by driving at times when they are less likely to be involved in a crash can earn a discount in the TripSense program,” said Mr. O'Malley.

Michele Strub-Heer, Progressive Direct Oregon product manager, said the company continues “to advance the science of auto insurance pricing. This program helps us to offer more accurate rates to more drivers.”

Progressive noted it introduced the first-ever usage-based auto insurance program in the United States in Texas in 1998, which used technology to gather information about how much, when and where a vehicle was driven in order to calculate usage-based auto insurance rates.

The test was successful in that it proved customers liked usage-based auto insurance because it saved them money and gave them control over their auto insurance costs.

However, Progressive ended the test in 2001 because of the high cost and logistics involved in installing the necessary technology.

Progressive Group ranks third in the nation for auto insurance and number one for motorcycle insurance based on premiums written.