Roland W. Anderson, the acting police chief of Weston, defended his officers' "absolute discretion" to decide whether to ticket - even whether to ticket unlicensed school van drivers. His view is echoed by many police chiefs.

Along with that tradition of police discretion in Massachusetts, police said, motorists have come to expect a break.

"On the East Coast, there's a strong culture that we've got a story," said Edward A. Flynn, state secretary of public safety and a former police chief in Braintree, Chelsea, and Arlington, Va. "And if we tell our story, only a really mean cop - or a trooper - will give us a ticket. And so there's a lot of that cultural thing going on and, let's face it, we draw our police officers from that culture."

Police officials also pointed to sharp increases in ticket fines over the years, a trend that they said has had unintended consequences.

Before 1983, the fine for speeding in this state was just $25 for a first offense. It went to $50 in 1988, when the Legislature established a graduated scale for higher speeds. Now the first 10 m.p.h. over the limit costs $100, including a $50 surcharge for a head injury trust fund, and each additional mile per hour over adds another $10. So driving 25 m.p.h. over the limit results in a $250 ticket. Insurance penalties add another $350 per ticket for a typical driver, the Globe estimated.

Those costs, police said, force officers into an all-or-nothing dilemma: Hammer drivers with heavy fines, or let them go unscathed.

Some officers enforce a compromise, by putting a lower speed on the citation, to save speeders the high fines.

"When I first came on the State Police in 1975, a speeding ticket was $25," said Major Dennis J. Galvin, deputy commander of the training division of the State Police. "Now look at it. You're looking at $300 at some points if you get stopped now. They've increased the fines tremendously. Does that have an effect? I think it does."

But while many police departments cling to the written warning, national studies have suggested that warnings fail to meet the basic test of traffic enforcement: changing a driver's behavior.

Massachusetts does have relatively safe roads, if only because they're so crowded that drivers have trouble getting up to high speed. The accident rate in the state is the lowest in the nation, per mile traveled, according to federal officials.

Still, as Massachusetts police continue to warn careless drivers, they might be tacitly encouraging deadly habits, said Peltier, the federal safety official.

"There needs to be some deterrent," Peltier said. "When the public knows that the law is being enforced, that's when you see behavior change."

'Personal system'

The expectation that officers will freely decide whom to punish and whom to warn isn't just a matter of local tradition. It is acknowledged in the manual for police academy instructors who train local police across the state.

The Massachusetts Criminal Justice Training Council manual describes ticketing here this way: "Every officer seems to have a personal system of deciding who gets a violation. Some talk about the attitude of the driver; some talk about giving a break to someone apparently in need; yet another officer said he never cited clergy, pregnant women, or soldiers."

Indeed, beyond a blanket allowance for drivers with medical emergencies - situations that would typically result in no ticket or warning - police officers said there are any number of drivers they are loathe to ticket: the elderly driver on a fixed income, the single mother rushing to day care, the driver who seems remorseful.

It is impossible to gauge precisely how Massachusetts police rank in leniency, because most states don't keep a count of warnings. Still, the level of warnings is much higher here than in the few other states with that information.

In neighboring Rhode Island, state and local police ticketed 62 percent of the drivers who received a traffic citation, according to a recent study by Northeastern University. In Connecticut, the figure was 63 percent. And in North Carolina, where state troopers handle most of the traffic enforcement, 80 percent of citations were tickets.

In Massachusetts, the use of warnings varies enormously from community to community.

In the state's toughest towns for speeders, nine out of 10 drivers got a ticket, even if they were town residents who might have hoped to catch a break from local police. That was the standard in Stoughton, Salem, Attleboro, and Lowell. In Stoughton, the strictest community, only 15 of 364 speeding citations were warnings.

By contrast, Needham, Quincy, and Newton were virtual havens for speeders, with nine out of 10 offenders getting warnings in the months examined. In Needham, the most lenient community, 171 of 179 speeding citations were warnings.

In one of the more lenient towns, a young, white speeder caught just such a break - albeit with an unusual condition attached.

Late for school one day in May 2001, John McQuown, 17, was speeding through his hometown, rural Uxbridge, when a police officer stopped him. He was going 72 m.p.h. in a 40 m.p.h. zone.

"I figured that was a ticket," said McQuown, now 19.

But the officer's response surprised him. "He said, `This is a pretty expensive ticket. It would be $300. But since you're late for school, I don't want to hold you up.' He said, `Have your parents call.' He wanted to make sure that I told my parents."

The police chief in Uxbridge, John E. Creighton, said he approves of his officers' tendency to warn, though he regards McQuown's case as "a hell of an extreme."

"The ticketing process is supposed to be used as an education," Creighton said. "If we can get somebody to slow down and change their behavior, that's all we're trying to do."

McQuown said the warning certainly did change his behavior. But since he got the warning, his driving record shows an accident in Walpole, and a speeding ticket in Millville.

In another traditionally lenient town, when a new chief tried to limit warnings, a court gave him a pointed reminder: In traffic stops, nothing trumps police discretion.

In February, Newton Chief Jose M. Cordero ordered officers to write tickets, and only tickets, in some areas where accidents were common. The police union told officers to ignore the order, then sued to overturn it.

"We didn't want to take away an officer's discretion," Cordero said. But "clearly here the discretion had gone too far the other way. Ninety-four percent - that's not discretion, that's abuse of discretion."

But last month, a Middlesex Superior Court judge, Associate Justice Leila R. Kern, declared Cordero's order illegal. The law granting police discretion is unambiguous, she wrote. "Whether there is a correlation between the number of accidents with citations versus warnings is not relevant." The city plans to appeal the ruling.

"Most of the chiefs that I've heard from can't believe the decision, that such a management decision is illegal," Cordero said. "It takes away our ability to organize a sound response to traffic safety concerns."

In defending the kind of discretion upheld by the Newton case, some police officials argue that the written warning also carries consequences.

Anderson, the acting Weston chief and a believer in police discretion, said, "A warning does go against you. ... After three warnings, your license is subject to revocation. A warning isn't just a piece of paper."

But in fact, the opposite is true. Contrary to the common view of many motorists and many police, the state doesn't keep track of written warnings, much less take action on them. Starting in the early 1980s, state law required the Registry of Motor Vehicles to suspend a driver's license for a week after the driver received three warnings in a year, following a hearing. But the Registry never kept track of warnings, and the law was never enforced.

In 2001, as Registry officials began the massive effort of typing in tickets and warnings to monitor for racial and gender profiling, they feared they would be required to enforce the existing law, including the cumbersome requirement of hearings. The Registry asked legislators to repeal the law, and they did.

Now, when warnings are issued, they are sent to the Registry and stored, by the millions, in a warehouse in Randolph. They are not noted on drivers' records.

Officers often don't bother to check the available information on a driver's history of tickets. And not every town equips cruisers with mobile computer terminals.

Still, officers on the streets could make better decisions if they knew that a driver had a history of warnings, several chiefs said.

The state would have to make that information available when officers or a dispatcher punches up a driver's history on a computer. Some towns do record their own warnings, but the information isn't available to police in the next town.

"That would be very helpful to us," said Edward F. Davis III, the Lowell police superintendent. Even when officers have that information, they don't always write tickets to drivers who have demonstrated recklessness. On May 17, 2001, an officer in the small town of Bellingham stopped an 18-year-old white man from Franklin for driving 36 m.p.h. in a 20 m.p.h. zone. Three weeks earlier, the driver had been ticketed in North Attleborough for drag racing and driving to endanger. But the Bellingham officer wrote a warning.

A ticket might not have changed that driver's behavior. He went on to be the most-ticketed driver in the state over the next two years, with 16 tickets in all.

Tomorrow: Fairest of the fair.