THE man was ''dealin''' on the boardwalk at Coney Island. As he was rolling marijuana ''joints'' to sell, he was surprised to find Police Officer Gina Scarda next to him.
''Where did you come from?'' he asked Officer Scarda as she snapped on the handcuffs.
The answer: by bicycle.
In the first five months of the year, some 600 bike patrol officers have made more than 90 arrests and issued over 16,000 summonses for moving violations, disorderly conduct, and violations like drinking in public or playing a car stereo at high-decibel level.
With such evidence that the bike police are effective, New York - with the largest number of two- wheeling cops in the country - has decided to expand the mountain-bike operation. Bike patrols operate in 29 precincts. The goal is to get a patrol in all 67 precincts. This could result in more than 1,200 police pedaling the streets.
''These patrols focus on quality-of-life issues and have proven to be a great tool in our fight against crime,'' says Police Commissioner William Bratton.
On Aug. 8, three bike-patrol police in Queens encountered three men fleeing an armed robbery. One officer, Richard Anderson, was hit by a slug from a .380 semiautomatic pistol. Fortunately, his bullet-proof vest stopped the round, and two of the suspects were arrested.
New York, which began using bike patrols in 1991, is not unique in turning to cops on wheels. This summer, Baton Rouge, La.; Santa Paula, Calif.; and Olivette, Mo., have sent out pedaling police for the first time. The International Police Mountain Bike Association (IPMBA), in Baltimore, reports that as of March there were an estimated 8,500 police on wheels in at least 572 communities.
The concept of police on bikes may have originated in New York in 1895 when Police Commissioner Teddy Roosevelt used bicycle patrols to catch people exceeding the speed limit with their horses. The police were so fast they were called ''The Scorcher Squad.'' The modern resurgence started in Seattle in 1988.
Jennifer Horan, the director of IPMBA estimates it costs about $900 to outfit a policeman on a bike. Gear includes a rack, lock, padded shorts, helmets, gloves, and eye protection. In the case of New York, the bikes and equipment were donated by the New York City Police Foundation, a nonprofit organization.
The police are enthusiastic about the assignment. ''People relate better to police on bikes than in cruisers,'' says Sgt. Max Tolentino, who serves as a coordinator for the Patrol Service.
Children are particularly attracted to the mounted patrols. ''It's great for the kids; they see you as a human being,'' says Dermot Whelan of the New York Housing Police, which has been using bike patrols since 1991. The bike patrols have been able to cut down on public drinking, which often leads to crime problems. ''People aren't hanging around as much,'' says Mr. Whelan.
The bike patrols also keep the officers fit. ''It sends the message, the more fit you are, the more professional you are,'' says Whelan.
At the IPMBA annual conference, bike-riding police compete in such events as carrying bikes over barricades and navigating a cone course at high speed.
A rigorous day of riding also keeps the officers alert. ''When I was riding in a cruiser, sometimes I would fight to stay awake halfway through a shift,'' says Whelan, ''but after a shift of riding the bike, I'm pumped up.''