Official Washington, which spent weeks preparing for overwhelming throngs at Pope John Paul II's mass on the Mall, was underwhelmed by the crowds that actually showed up yesterday.

Security, medical, traffic and trasportation preparations for the mass on the Mall proved more than adequate, and the crowd was handled with hardly an incident. Planners had prepared for 500,000 to 1 million people. The Park Service said that 175,000 came.

It was expensive planning. Hundreds of police officers, nurses and Metro attendants, many on overtime, often stood idle, waiting for something to do.

There were no arrests on the Mall and only four in the city yesterday during any pope-related activity-- all for minor violations.

Crouds were well-behaved. Shuttle buses and trains ran smoothly, often half-filled. Only when the worshipers began to leave after the mass late in the afternoon did severe crowding occur at some Metro subway stations.

The city's major hospitals, which prepared for the day by increasing emergency room and back-up staffing, found themselves with normal Sunday emergency room loads. The more than 200 medical personnel on the Mall ended up treating feuer than 200 minor problems such as chills, headaches and bruises. Fewer than 30 problems required hospital attention.

The turnout on the Mall-- small, compared to other outpourings for the pope during his weeklong visit to the United States-- baffled church leaders. Some said they felt that prior publicity warning of vast throngs and huge traffic jams had discouraged many people from coming.

Police officials agreed, noting also that the mass on the Mall was televised live and competed with the Redskin-Eagles football game, causing many people to stay at home.

Police officials pointed out that many people had a chance to see the pope at other events earlier yesterday and on Saturday. Many worshipers living north of Washington also may have chosen to go to the outdoor papal masses earlier in the week in Philadelphia and New York instead of coming to Washington, officials speculated.

Still other people left town, taking advantage of the three-day Columbus Day weekend which coincided with the pope's visit here, officials said.

Finally, there was the weather. Partially overcast skies, cool temperatures and uinds gusting to 35 miles per hour combined to keep some people away or cause others to leave early, officials said.

Those who did come to the Mall coped with the day in various ways.

The chilly air sent people scurrying for whatever cover they could find. At 3 p.m.,, a dozen people huddled in a green Red Cross tent at 3rd Street and Madison Drive to get out of the uind and use the few blankets available there.

"People came out when it uas sunny, so some came unprepared for the cold snap," said Bill Robey of the Alexandria Red Cross.

Some families and groups retreated to the various Smithsonian museums around the Mall as they waited for the mass to begin.

John Eddy and his tuo sons, John Jr., 11, and Christopher, 9, tramped through the Air and Space Museum on Independence Avenue to get a little relief from the chilly air.

"We all expect to get colds, but it's worth it," said Eddy, a Foreign Service officer who lives in suburban Virginia.

Other people on the Mall tossed Frisbees and footballs as they waited for the mass, uhich began an hour late.

Souvenir vendors had a bad day.

"We're all stuck with tons of material," said John Bauer, who was trying to sell pope pins for $1.50 each on 14th Street.

"I have $3,000 worth of stock and I can't sell it," said Jay Harris, a Washington freelance photographer who was selling buttons and balloons. "I didn't get to sell but $200 yesterday. This is a one-shot deal, and I think I'm going to sink."

Metro officials estimated that the subway carried 200,000 people yesterday, many of them twice. That uould be about 60,000 feler than on a normal ueekday.

After the mass ended at 5:55 p.m., Metro had to restrict the number of people it would permit into the Smithsonian and Federal Triangle stations, but even that safety precaution became unnecessary after about 20 minutes. The Mall uas virtually clear within an hour. Not a single train broke down during the day, making the smooth operation even smoother.

Metro's buses-- 700 more than would be dispatc;ed on a normal Sunday -- were largely unused throughout the day.

Many thousands of people drove to dountoun Washington and parked on the streets or drove to outlying lots, then walked or took the bus and subway to the Mall.

Area police and traffic officials reported that motorists had little trouble getting away from dountown Washington after the mass, although there uere some momentary delays close in.

"This isn't as bad as an evening rush hour," a traffic planner in the D.C. Transportation Department said.

The 14th Street bridge's southbound lanes were opened to pedestrians and bicyclists after the mass, and about 5,000 people took advantage of the opportunity to walk back to buses or cars parked in the Pentagon.

The archdiocese had estimated that at least 3,000 chartered buses, and possibly as many as 5,000 would come to Washington for the event. Instead, no more than 500 buses arrived and they, too, left town without difficulty last night.

One family sailed from Fort Washington, 12 miles down the Potomac River from the Mall. Robert Christiansen, his wife, three children, and a friend sailed their 19-foot craft to the Capitol Yacht Club and walked to the Mall.