THE BAY Area Toll Authority has discovered yet another flaw in the FasTrak system that favors toll cheaters. The new culprits are drivers of rental cars without transponders through FasTrak lanes across the seven state-owned bridges in the Bay Area.

Apparently, rental cars sail through the FasTrak system with no recourse because the drivers do not own the cars and it would be difficult and expensive to track them down to collect the $4 toll.

It might sound trivial, but the authority says approximately 120,000 rental cars a year cross bridges for free.

Normally, car owners who cheat have their license plates photographed and a bill is sent to the address of the registered owners. That's in a perfect world.

But FasTrak is far from perfect as we've documented in a previous editorial. It can be exploited by people who drive new cars or recently purchased used cars with no license plates, for example. To top it off, we question the accuracy of many photos taken.

Now it's rental cars. The toll authority hopes to beat these cheaters by bringing in a network called PlatePass, which has experience with FasTrak-type settings.

According to reports, PlatePass' role is it will pay tolls automatically from each Hertz, Avis and Budget rental car that crosses the bridge without paying. PlatePass, in turn, will recover the $4 toll plus a $1.50 or $2.50 fee from rental car companies. Then rental car companies will charge the renter to make up for the loss.

Unfortunately, not every rental car company is included in the toll authority plan so some cheaters will get through, which calls into question how many cheaters will actually be caught or deterred by this new arrangement. But the toll authority is stuck. It doesn't have the power to require every rental car company to carry FasTrak transponders and have drivers billed when they are finished with the car.

This exposes another flaw in FasTrak that wasn't considered when the system was created.

Face it, unless a team of Highway Patrol cars are standing by at each bridge, cheaters will get away with beating the FasTrak system and hundreds of thousands of dollars will be lost every year.

Bottom line, FasTrak is a flawed system that needs a great deal of improvement and refining.