Hundreds of Virginia motorists using I-66 as a quick method of commuting to work got a rude surprise yesterday as police started a major crackdown on violators of rules requiring at least three persons in each car during rush hours.

In the morning and evening rush hours, Arlington police issued tickets to 239 drivers, while state police ticketed 214. The tickets can carry $35 fines and three points toward suspension of a driver's license.

Police said the crackdown was triggered by widespread disregard for the so-called HOV (High Occupancy Vehicle) regulations that are designed to reserve the stretch of I-66 between the Beltway and Rosslyn for carpoolers.

"We do this periodically, but we're going to keep doing it now until something changes -- until the violations are reduced down to nothing, or until they change the law," said Virginia State Police Sgt. Michael Clem. He added that the likelihood of a change in the regulations, made by the U.S. Department of Transportation, "is almost nothing."

Police slowed traffic with safety cones and flares so that they could count passengers. "It wasn't a total stop in most places," Clem said.

One car coming through appeared to have a mannequin inside -- a device occasionally used to beat the system -- but by the time troopers noticed it, the car was too far down the highway to stop. "If they'd like to come through again tomorrow, we'd be glad to oblige them," Clem said.

He also said he believed that some of the offenders had been ticketed for HOV violations before, but that with so many involved, it was hard to tell.

The reaction of those stopped and ticketed was mixed, Clem said. "You get some people who won't say anything, then you get some people who want to try the case on the side of the road," he said. "They don't always understand that we enforce the law, but we don't hear the case. The judge hears the case."

The biggest crackdown effort by the state police in both the morning and evening was on the stretch between the Beltway and Rte. 7 (Leesburg Pike).

Two troopers also slowed motorists at the Route 7 entrance ramp to I-66 eastbound yesterday morning. Usually, this ramp is not patrolled. Other troopers checked the Dulles Connector Road, as it feeds into I-66 eastbound.

"Generally, these are the major places where we have violations," Clem said.

Clem said 15 state troopers, instead of the usual three, were assigned yesterday morning to I-66 inside the Beltway.

Cpl. John Haas of the Arlington police said he had eight officers stationed at the county's I-66 ramps, checking cars and waving suspected violators on to the shoulder.

Haas said Arlington police periodically check the ramps for HOV violators, but are stepping up their enforcement at the request of state police from now until Friday, and between March 18 and 22.

Clem said that while the crackdown officially began yesterday, state police ticketed 122 violators during a routine 4 to 6 p.m. rush hour check on westbound I-66 last Thursday.

Does he think the crackdown will succeed in clearing the road of HOV offenders? "We hope," he said. "But, then, we hope to get rid of drunk drivers and we hope to get rid of speeders. It's kind of an optimistic view."

HOV restrictions are in effect on I-66 eastbound, between the Beltway and Rosslyn, from 7 to 9 a.m., and on the same stretch of I-66, westbound, between 4 and 6 p.m. Those who use the highway to go to and from Dulles International Airport are exempted from the restrictions.

The seriousness with which HOV violations are viewed is indicated by the penalty of three license points. Virginia residents who accumulate a total of 18 points during any 12-month period can receive a suspension of their licenses for three to six months.