Would you let an insurance company scrutinize your driving habits - and whether you speed on the Beltway - if you could save money on premiums?

Innovative "pay-as-you-drive" programs now offered in Maryland are being touted as a way to equalize premiums, lower costs for safe drivers and get people to drive less. The programs use electronic or other measurement devices to record mileage patterns, as well as when and how drivers use their vehicles - and charge premiums based on those habits.

"On its face, this is probably one of the most revolutionary ways to price insurance in this country," said state Sen. Lisa Gladden, a Baltimore Democrat who has been a proponent of pay-as-you-drive insurance in Maryland. "Why should my insurance rates be as high as the two-time drunk driver or the guy who speeds?"

But critics such as the American Civil Liberties Union say the electronic monitoring raises privacy questions and may be too intrusive. And such programs could boost insurance costs for people who put on a lot of miles or drive aggressively.

Until now, most programs were limited to pilot efforts by small companies, but a handful of larger insurers have started to offer them.

Progressive, for example, is rolling out a pay-as-you-drive program using technology that tracks mileage, the time of day a car is used and driving behavior such as abrupt braking or fast speeds. So far, Progressive offers the program in six states, including Maryland.

"Drivers who don't use their vehicles that much or are safe drivers deserve a benefit for that," said J.C. Jones, a product manager for Progressive.

Policyholders plug a wireless device into a port under their steering wheel column - something available in models built in 1996 or later. The device, which costs $30, sends information to Progressive, recording time of day, miles driven and speed.

Customers who want to shape habits to reduce premiums can check their driving data on a password-protected Web site. The company declined to detail how many people have signed up for the program, which began this year.

Customers receive a score based on patterns of behavior over time. At the end of six months, their insurance premium could fall by as much as 40 percent, Jones said. But drivers who put excessive mileage on their cars, drive often at riskier times, such as after midnight, or make a habit of braking hard or accelerating quickly could find premiums rising, he said.

Aldora Cureton, a 46-year-old home day care operator from Belair-Edison, signed up for Progressive's program for her Ford Explorer about a month ago. She hopes to lower her $187 monthly premium.

"I drive at the speed limit, even though there are so many fast drivers trying to get you to drive faster," Cureton said. "You have to watch the crazy drivers out there. I'm cautious, and I hope this will help me to save money on my insurance."

Progressive's program is the first offered to Maryland drivers, said state insurance commissioner Ralph S. Tyler, who approved it. None of Maryland's biggest insurance companies - Geico, State Farm, Allstate or Nationwide - has moved to offer a pay-as-you drive option, he said. Pay-as-you-drive types of insurance could gain traction in the coming years, because the benefits also appeal to policy-makers, said Jason E. Bordoff, policy director for the Hamilton Project at the Brookings Institution.

Brookings research shows that pay-as-you-drive options could save two-thirds of drivers money on their auto insurance. Drivers would save, on average, about $270 per vehicle annually.

"Now ... the high-mileage drivers are subsidized by the low-mileage drivers," Bordoff said.

And incentives to reduce driving will lead to reduced oil consumption, greenhouse gas emissions, road congestion and accidents, his research showed.

"This is starting to come into the mainstream," said Michael Replogle, transportation director for the Environmental Defense Fund. "It can provide a way for motorists to basically drive in a greener way and save money at the same time by driving fewer miles and by driving more calmly."

But some worry that electronic devices in cars could invade privacy in ways that drivers may not even realize.

Barry Steinhardt, director of the ACLU's technology and liberty program in Washington, said that no laws exist to prevent police or others from accessing such data. The ACLU does not oppose the technology, but its leaders think that the U.S. needs overarching privacy laws.

"Basically, we're paying people to give up their privacy," Steinhardt said. "We should have rules that say data that's collected for one purpose cannot be used for another purpose.

"We have the capability to track individuals - not only how fast they're driving, but when they're driving and where they're driving, and that's frightening," he said. "We are on the cusp of creating a surveillance society where our every action, our every movement is going to be tracked. This just brings us one step closer."

Progressive officials say their program does not track a driver's location or where they travel. But GMAC Insurance last year began offering discounts on premiums to OnStar subscribers who allow the insurer to track their odometer readings. California's insurance commissioner recently proposed regulatory changes that would open the door for usage-based insurance programs. But the commissioner has said he will not approve programs that give a driver's location through tracking devices.