On Sundays and weekday rush hours, it is standing-room-only on Peking's main subway line as people jostle for breathing space.

Before each station, the broadcast announcement cautions against pushing or shoving, but no one seems to pay attention.

As the train pulls into the station, the crowd surges forward, doors jam, and after several uncomfortable minutes of squeezing and, many times, fistfights, the train pulls out of the station.

The habits that have become part of daily life on the buses and trolleys above ground have been transferred to the underground rail, as the subway is called.

The crowds on this main line -- not only commuters but also out-of-town passengers laden with luggage -- are the most recent manifestation of Peking's growing public transportation problems.

As the demand for public transportation increases and strains on the inadequate network of buses and trolleys increase, some officials say the subway is one of the few places left to expand to accommodate Peking's public transportation users.

Peking is the only city in China with something close to a subway system.

Tianjin, 75 miles to the southeast, has one line, and many of the other major cities, such as Shenyang, Shanghai and Zhengzhou are developing their own plans.

In Peking, the main line runs for about 15 miles on an east-west axis from the Peking railway station to the western outskirts.

The recently opened second line makes a 10-mile half-loop around the northern part of the city, but the two do not connect.

Currently, subway ridership makes up only about 5 percent of the total 7 million daily ridership of all public transportation.

But authorities say they expect that proportion to increase as more subway lines are built and more residential and office complexes go up along the routes.

The long-term plan, they say, is to build another six lines that would crisscross the city for a total of 146 miles.

The success of that plan remains to be seen. So far, the track record of the underground rail has not been good. It has been plagued by enormous cost overruns, lengthy construction delays, generally poor planning, and, recently, late trains -- all characteristics that have been used to describe some of its counterparts in major western cities.

For example, the second line that opened in late September began operations three years after it was completed, eight years behind schedule and at more than double the original cost.

Part of the delay was caused when many of the construction workers were sent to Pyongyang to help North Korea build its subway, according to reliable sources.

Although the tunnel and rails were finished in 1981, there were many technical problems.

Nearly 20 power stations, more than 600 pieces of operating equipment and more than 8,000 pieces of communications equipment and various other devices had to be replaced.

Moreover, it is expected to take at least another two years before the new line can connect with the main line via a terminal yet to be built in the center of town.

Authorities blame the problems on the chaos of the 1966-1976 Cultural Revolution. "Now the different authorities have reached the conclusion that the subway is a great help," said Li Jianguo, deputy manager of the Peking Subway Co., which took over the management and planning in 1977.

"The subway is the only way left to expand to accommodate the great amount of people" who use public transportation, he said. "The above-ground transportation is near full to capacity and we can only adopt temporary and coercive measures."

These measures, which include shifting truck traffic to nighttime and staggering the work schedule of different offices, are not going to do much for the long-term traffic situation.

A recent article described Peking's traffic headache as one where "bicycles, like an endless stream, flood the roads. Overcrowded buses crawl bumper to bumper.

Passengers wait impatiently, then push and shove to get aboard." Like many other major cities, Peking's growth rate for public transportation has lagged far behind the need.

So far, the subway has cost the equivalent of about $384 million. But it is far from complete.

The first line, completed in 1969 after four years, cost about $7 million per mile, deputy manager Li said.

Construction of the second line began in 1971 and cost closer to $17 million per mile.

By comparison, Washington's Metro rail system is about 60 percent complete and eventually is supposed to have 101 miles of track. The estimated total construction cost is $9.2 billion, and the average number of rides per day is more than 350,000. Generally, Metro rail covers more than 60 percent of its operating costs; the rest is made up in subsidies from the federal and local and state governments.

Peking, however, only recovers about 30 percent of its operating cost. The remainder is covered by the state Ministry of Finance, Li said.

Li acknowledged that the subway, has had its share of problems. Before 1981, there were widespread reports of people riding the subway free by abusing a special pass privilege given to workers who still needed to do construction work on the line.

The subway costs about four cents to ride. Li said the practice was discontinued in 1981 after it was found that many of the 6,000 passes were being abused.

Now, the main problem is to relieve congestion on the main line and increase ridership on the new one, he said.

Authorities have added more trips to the main line and hope the completion of the connecting terminal in the center of the city will help the problem.

At its peak, the ridership on the main line has reached 470,000 daily, compared to the 30,000 to 40,000 daily ridership when it first opened in 1971. The new line now has a ridership of 30,000 to 40,000, although authorities hope it will grow to 120,000 eventually.

The subways are relatively clean and safe, compared to some of their western counterparts. There is no graffiti in the station or on the subway cars. Instead, billboards advertise products including socks, Penguin brand electric fans made in Shanghai and Vitamin E.

Modeled after those in the Soviet Union, the subway platforms are wide with broad columns and walls faced with artificial marble. The plan is to have paintings of different Chinese landscapes adorning the walls along the new line.

In the subway cars, there are overhead straps for standing passengers and posted signs prohibiting smoking and promoting hygiene.

On the more crowded main line, the announcer usually urges passengers not to shove, not to spit, not to throw fruit skins on the floor and to give priority to the elderly and young.

But, as one elderly woman complained recently, "There is no broadcast when they have to keep making these unscheduled stops between stations and make us wait a long time."