'Denver Boot' survives despite legal challenges, irate motorists

''That's a hit.''

The two-way radio crackles with confirmation that the license number of the car Joe Petitpaf is double-parked next to does indeed belong to a motorist who has failed to pay overdue parking fines.

''Do your thing, Fidel,'' says Mr. Petitpaf to co-worker Pedro Castro, nicknamed Fidel.

Mr. Castro hops out of the parking department station wagon, grabs a yellow cast-iron contraption from the trunk, and in less than a minute, he has ''booted'' another Bostonian.

Use of the Denver Boot - a device that locks over a car's tire, immobilizing the vehicle until the payment of past parking fines affects its removal - is gaining popularity with police from coast to coast. At the same time, legal objections to it are mounting.

''I see the use of the boot skyrocketing,'' says Steve Emory of Hersey Products in Dedham, Mass., one manufacturer of the boot. ''Cities have a lot of outstanding parking tickets. With the economy the way it is, it costs much more to have a car towed than booted.''

From Denver, where the boot originated, use of the ''auto cuff,'' as it is also known, has spread to Boston, Washington, D.C., and a number of smaller towns. Other cities considering its use or employing it to a lesser extent include Detroit, Houston, New Orleans, Baltimore, Los Angeles, and Philadelphia. New York City has begun a pilot project involving the use of some two dozen boots.

But lawsuits follow as closely on the heels of the boot's spreading use as a car clings to the back of a tow truck. Although cases generally deal with booting procedure and the right of a motorist to a hearing on the booting, there are some who advocate a complete ban of the boot.

''I think it is a legitimized form of extortion,'' says Richard Rose, a Denver lawyer whose client sued the city because of a booting incident. ''I would like to see it ruled unconstitutional.''

While Mr. Rose concedes there is little chance of that, others dismiss the idea outright. ''There may be a few procedural bugs that have to be worked out in court, but continued use of the boot is undeniable,'' says Denver County court adminstrator Kenneth Goodman.

In fact, that is the scenario that has unfolded in Denver and Los Angeles. In Denver, Mr. Rose's client sued the city, claiming that he wasn't told he had the right to contest the booting he received. The court ruled in the driver's favor, as did a Los Angeles court in a similar case. But in both instances the cities simply changed their procedures to satisfy the courts, and the booting went on as before.

''There are misconceptions about the boot's use,'' says Mr. Goodman. ''It is not used capriciously. It is based on a formula and a procedure.''

The procedure generally follows this pattern: Once a motorist has accrued a specified number of unpaid parking tickets (generally three to five), and a time period in which the vehicle owner may protest the tickets has passed, the car is eligible for booting. The license number of the car in question is printed out on a computer list with other violators. Parking officials use the printout to check the licenses of parked cars at random, booting when they find a match.

''We have a sound system that doesn't take advantage of innocent people,'' says Paul Davis, a parking official in Washington. In another case there, the court ruled in the city's favor, saying the city had legitimate reasons to boot. ''The court decision upholds the principle of what we're doing,'' says Mr. Davis.

A different view is voiced by some who have been booted. ''How am I supposed to do my job? There's no place to park in this city,'' complains Boston plumbing contractor Richard Connelly, who had accrued more than 100 unpaid tickets when his vehicle was booted. He is pressing a suit against the city on procedural grounds, not on the overall use of the boot.

Few challenge the effectiveness of the boot in staunching the flow of unpaid parking violations. In Washington, where 700 boots are in use, Davis reports the voluntary payment rate has risen to 70 or 80 percent since the city started booting in 1973, up from approximately 50 percent.

In Boston, only 16 percent of all parking tickets issued were paid before use of the boot was initiated. Now close to 50 percent of the tickets are being paid. In Denver the percentage of those paying fines has risen from 40 to 90 percent.

Not all of those were paid for by motorists forced to settle up by the boot. Officials believe the highly visible nature of boots is an effective deterrent to would-be ticket dodgers.