Some Virginia drivers are getting free rides on the state's toll roads, and it's costing the state as much as $100,000 a year.

The problem, state officials said, is that some Virginia license plates can't be read by cameras at the state's toll booths.

About 2 percent of the 1.5 million license plates reviewed by the state in a recent study had a design or color combination that made it nearly impossible for toll booth cameras along the Dulles Toll Road and elsewhere to read the tags. That means a driver without an E-ZPass can sail through an automated toll collection lane without paying -- and never get a bill or fine in the mail.

Some Virginia license plates that toll cameras can't read:
» Shenandoah National Park Association
» Drive Smart Virginia
» James River Park System
» Scenic Autumn

The Virginia Department of Motor Vehicles declined to say which plates can't be read, but an agency study indicated they were typically specialty plates with busy backgrounds. Among those the study identified were plates representing the Shenandoah National Park Association, which features mountains, a bear and full-color background, and the Drive Smart Virginia plate, whose background logo makes the tag numbers difficult to read.

"The challenge that we've got -- and many other states have it as well -- is that we've gotten into very colorful, full-background-designed plates, which obscure the letters," said DMV Commissioner Rick Holcomb. "We're finding that law enforcement is having some difficulty reading them, and the toll facilities are having a challenge reading them as well."

The DMV's study showed that the state was losing as much as $100,000 a year in uncollected tolls because of the plate problem.

Maryland can't collect on about 5 percent of toll violators whose tags are photographed by toll booth cameras, but it's not because of a problem with the plates themselves. The biggest problem Maryland faces is drivers who cover their license plates, Maryland Transportation Authority spokesman John Sales said. A Maryland State Police spokesman said police don't have trouble reading Maryland license plates.

Virginia has no plans to recall the unreadable plates. Nor will it stop issuing those that can't be read because many of those specialty plates raise money for nonprofit causes, officials said.

"Recalling the plates would be an administrative nightmare," said Del. Joe May, R-Leesburg, chairman of the House Transportation Committee. "It's easier just to do it by attrition."

Instead, the state is pursuing new technologies that would make it easier for plates to be read by the toll booth cameras. Those include electronic bar codes that can be added to the plate, making the tag's design irrelevant.

"You couldn't see it with the naked eye, but it could be read by law enforcement or electronic toll enforcement," Holcomb said. "We're going to study that, because there are some privacy concerns we need to address. But that seems to be the solution."

Still, Holcomb said, that technology is at least a year away.