The scores are based on incidences of speeding, and harsh cornering, braking and accelerating, and they parallel the scores in FMCSA’s Compliance, Safety, Accountability program, said Chris Carver, program manager of Onboard Advisor with Liberty Mutual Agency Corp., Boston.

A fleet that scores 50 is in the 50th percentile, “better than 50% of the fleets out there,” Carver said, and a fleet that scores 30 is “better than 70% of the other fleets out there.”

The software weighs such factors as type of road, weather and traffic. “There’s a big difference between someone going 10 miles an hour over a speed limit on an open highway” when surrounding vehicles are traveling at the same speed, versus a driver “swerving in and out of traffic on a secondary road in a fully loaded truck,” Carver said. Driving one way or the other is “how you get your score to go up and down,” he said.

Thornton said that Comfort Flow’s scores showed enough improvement during 2010 that its insurer reduced its rates for 2011 by 10% to 12%.

Through November, no driver had a score of 50 or higher, Thornton said, which means the company’s drivers are driving better, with fewer risks. As a result, Thornton said, he expected Comfort Flow’s insurance rate for 2012 to decrease as well.