The gray-haired man in the green shirt and plaid pants was walking through downtown Silver Spring, minding his own business, when he noticed the armed men on the big horses. His face broke into a big grin as he waved and yelled his approval to the mounted police patrol:

"That's the way to do it!"

Officer Richard Pelicano and his partner, Steve Tucker, are accustomed to such enthusiastic responses when they patrol the Montgomery County park areas under the jurisdiction of the Maryland-National Capital Park Police. The force has 16 horse-mounted officers in Montgomery County and 16 patrolling the parks in Prince George's. In Montgomery, horse patrols have been used for more than a year in Silver Spring, which is ringed with six parks, but they have been working other parks for nearly 20 years.

Other police forces also have found horse patrols useful. The U.S. Park Police, for example, has a stable of horses that officers use in the Washington area to patrol park areas. And the Secret Service and some other local jurisdictions keep mounted patrols.

"The horses are like a magnet," said Pelicano, 33.

"People come and talk to us when they see the horses," he said. "That makes it easier for us to get information about what's going on in the park areas. If we were in a patrol car or even on a motorcycle, it would be harder because people couldn't get to us."

The horses help make the police presence more visible, he said. "We think that has the effect of cutting down park crime, such as drug use and theft, because the criminals see us around and then don't do what they may have intended to do."

Some critics, however, suggest that the mounted patrol is more effective as a public relations tool than a crime deterrent.

"It's showboating," said one Montgomery County police official, who asked not to be identified. "We don't care if they do it," he said, "but we don't think it does much good."

But Maryland-National Capital Park Police officials say they have statistics proving that the use of horse-mounted officers has helped curb crime in the parks.

During the first nine months of 1984, for instance, three sexual assaults were reported in Silver Spring parks, according to park police spokesman Tim Boyle. But since mounted police began patrolling those areas in late 1984, no sexual assaults have been reported, he said.

Serious offenses such as robbery also dropped during that period for those park areas, Boyle said, decreasing from 36 to 31. The number of weapons violations, such as illegal possession of a gun, declined from 20 to 15, he said.

Meanwhile, alcohol violations in those parks have increased from 150 citations, when the areas were patrolled exclusively by officers riding in cars, to 280 citations in the period since the mounted patrols were added, Boyle said. "We think we are seeing more alcohol citations because our patrols have increased," he said.

Pelicano and Tucker say the horses help them deal with the most common park crimes, such as drug use, theft and indecent exposure, because they can reach areas that patrol cars cannot, and because on a horse they are more intimidating than foot officers.

In one recent incident, police acted on a tip that there would be a confrontation between two youth gangs by assigning mounted officers to a stakeout position near the site of the scheduled meeting.

"The kids arrived, saw the horses and just melted away," one officer said.

There are disadvantages to using horses for patrol, however. Officers on horseback cannot move as fast as those in patrol cars; so if something happens in a park that requires immediate attention, the mounted patrol cannot easily re- spond. Criminals on motorcycles and in cars can outrun mounted police.

Although no park police have been shot in Montgomery County while patrolling on horseback, Pelicano, as a precaution, wears a bulletproof vest when he goes riding.

"You never can tell," he said.