Make sure to check your Fast Lane bill

Up to a million users have been charged a higher fee.

The Pike has pulled a fast one on potentially thousands of FastLane users, slipping truck-sized charges onto their bills after their cars were electronically mistaken for bigger rigs.

The hefty fees - in some cases more than double what drivers were meant to pay - have been applied to as many as 1 million FastLane transactions at a time when tollpayers are already digging deep, according to a Turnpike audit.

“The reality is the technology that reads the number of axles is at least 10 years old. We recognize we need to replace a lot of our infrastructure including this technology,” said Jennifer Flagg, the Pike’s chief administrative officer.

The revelation comes a day after board members approved a $2 hike in tolls in the tunnels and a 25-cent hike at the Allston and Weston tollbooths.

Flagg said FastLane cameras are 99 percent accurate, but during bad weather the camera meant to read the number of axles on a vehicle can be covered with grime or snow and misread its target.