The monthly invoice could look something like an electricity bill or a cellphone statement. But instead of kilowatt hours or roaming minutes, it would itemize how many miles you drive - with surcharges for traveling during peak hours, premiums for using so-called Lexus lanes that bypass rush-hour snarls, and discounts for sitting through traffic jams.
The free and open road, regarded by many Americans as a birthright, could become a relic under a plan being discussed in Massachusetts and in several other states, transforming highway use from a service available to all into a utility paid for on a per-mile basis.
This philosophical shift is the cornerstone of a landmark report, released last month by the Commonwealth's Transportation Finance Commission, which was tasked with finding the estimated $15 billion to $19 billion needed to fix the state's crumbling roads and bridges over the next two decades.
Under the commission's plan, a 5-cents-per-mile fee on major roads would replace, or minimize, gas taxes and fundamentally change a central aspect of everyday life.
"The idea that this is completely free is a fiction. It isn't," said James Aloisi Jr., a lawyer who served on the commission and a transportation official under former governor Michael Dukakis. "Someone's got to pay for it. We think the user should pay for it."
But early signs show that regular drivers may find the notion of a fully-tolled highway system harder to fathom.
"The taxpayers pay taxes to build the roads, we pay tolls to use the roads, and now they want to hit the taxpayers again," said Phyllis Lachman, 67, of Concord.
State Senator Steven A. Baddour, a Methuen Democrat and cochairman of the Legislature's transportation committee, said turning roads and bridges into a utility and adding more tolls "is too big of a stretch."
"People don't see it that way," he said. "You can't just put it in a report and expect people to buy it."
The technology that allows per-mile pricing is being used around the country, in bits and pieces, though no state has begun tolling all major roads. Oregon has come the closest, with a pilot program that equips volunteer drivers with global positioning devices in their cars. They pay by the mile and are exempt from gas taxes.
British drivers famously pay a flat fee equivalent to about $16 to drive into central London. If they fail to pay in advance, a security camera will shoot a picture of their license plates and automatically send them a ticket. Mayor Michael Bloomberg of New York is pushing for a similar approach in his city.
More commonly, several states are using transponders, the same ones Massachusetts drivers use for the Fast Lane program, to create premium lanes on major highway systems that set pricing based on supply and demand. Those willing to pay hefty tolls get home the fastest.
Drivers on an 8-mile stretch of Interstate 15 in San Diego pay $1 to $4 to use the carpool lane (carpoolers and buses still ride free). Digital signs display toll prices that change throughout the day based on traffic volume. An express lane on State Road 91 in Southern California costs as much as $9.50 for a 10-mile drive during peak hours.
The price of using the lanes rises during rush hour so that drivers willing to pay more get a faster commute. At first, critics derided the roads as "Lexus lanes" because it was believed only the rich could afford to use them.
But researchers have found popularity cuts across class lines. Parents desperate to avoid a late fee from a day-care center or workers about to get fired for tardiness do the math and decide that a pricey ride can bail them out in a pinch. San Diego is expanding its program.
"That's the most free-market way of doing things in transportation that we have," said Martin Wachs, director of transportation, space, and technology for the Rand Corporation.
To Wachs, these lanes illustrate the broader choice drivers have. They pay for faster-moving, higher-quality roads through user fees or they pay by sitting in traffic on patchy, slow roads.
"You don't pay the same price for a hamburger as a steak," he said.
The Bush administration has embraced the theory as well. Last month, US Transportation Secretary Mary Peters awarded grants worth $848 million to Miami, Minneapolis, New York City, San Francisco, and Seattle to fight gridlock with strategies that include high-priced rush hour lanes.
The Massachusetts Turnpike Authority has been studying cameras that record license plate numbers, so that motorists who drive through toll booths without a Fast Lane transponder get a bill.
The authority is also looking at Fast Lane equipment that lets motorists drive through toll booths at highway speeds rather than slowing to 15 miles per hour.
The technology, in place elsewhere, would give the Turnpike Authority more options to set aside carpool lanes for fast travel.
Or the authority could charge higher tolls on regular lanes during rush hour. That might reduce congestion by persuading commuters with flexible schedules to avoid rush hour.
In most cases, traffic planners choose to build new lanes or convert carpool lanes into Lexus lanes instead of charging everyone. A more dramatic change, charging for basic roads that are now toll-free, may prove a larger hurdle. The federal government forbids charging on interstate highways, meaning the discussion to change would have to take place on a national level. And any system that requires all drivers to log their travel would raise privacy concerns. Proponents say there are ways to overcome the concerns - including systems that let drivers register for anonymous accounts or keep their digital driving logs stored in their cars.
But unless those concerns are allayed, many politicians say they will not support turning roads into utilities.
Voters "simply don't want Big Brother," said Representative David Paul Linsky, Democrat of Natick. "I want to see a specific proposal."
Nonetheless, the market approach has attracted support from the political left and right. Environmentalists say letting drivers see the true cost of using the roads will discourage congestion and persuade more commuters to use public transportation or to carpool. On the other hand, free market libertarians see an opportunity to reduce taxes and involve private companies in building, maintaining, and controlling roads.
"We use economic markets for electricity, for telephones, for food, for water . . . the question is why roads should be excluded," said Gabriel Roth, a research fellow at the Independent Institute and editor of the book "Street Smart."
The American Automobile Association, a powerful consumer lobby, has traditionally opposed adding tolls. Art Kinsman, director of government affairs for Southern New England, said he will poll his 2 million members. But if drivers are expected to treat roads as a utility, they will need to see better services. Now, many accept it may take a few months to fix a pothole. If drivers pay by the mile, they'll demand to know, "are they going to come out and fix it tomorrow?" Kinsman said.
Beyond that, motorists need confidence that the money will be going to improve the transportation network, Kinsman said.
"There needs to be some trust restored with the public," he said. "I think it's a tremendous shift in how people view roads."