Metro's top manager said yesterday that he will monitor conditions in subway stations on weeknights after 10, when Metro is trying to save money by running shorter trains, and will restore longer trains if crowding is a problem.

"If it requires us to keep all or part of the system at four-car trains instead of breaking them down [into two-car trains], that's what we'll have to do," Metro Chief Executive Richard A. White said.

White made those comments as complaints from the public poured in to the transit system and a Metro board member questioned the wisdom of the new policy.

This week, Metro cut the length of trains in half, from four cars to two, on every line after 10 p.m. Sunday through Thursday. Metro expects the plan will save $1 million a year in reduced electrical, labor and maintenance costs.

White said Metro workers will count the number of passengers boarding trains after 10 p.m. next week. He said he would restore the four-car trains if the stations were busy and if short trains would mean some passengers would be left on platforms.

That was exactly the condition Tuesday night at the Metro Center Station between 10:30 and 11 p.m.

Passengers were unable to squeeze onto jammed Orange and Blue Line trains and had to wait 15 to 20 minutes to try to board the next train. Many riders mentioned ruefully that the trains shrank the same week Metro began charging higher fares and fees.

"We're paying more and getting less," said Donald Center, 23, of Centreville.

Since the policy took effect, it has created a late Metro crunch, especially on the heavily traveled Red Line in downtown Washington. At the Farragut North, Metro Center, Gallery Place-Chinatown and Union Station stops, angry crowds have found themselves competing for space on the late trains.

The crowding has caused some schedule delays, and several riders complained about missing connections to buses. By the time her two-car Blue Line train reached the Addison Road-Seat Pleasant Station stop on Monday, Karen Hayes had missed the last C26 bus of the night. She and a friend had to spend $15 on a cab ride home. "The train was, like, 10 minutes late," said Hayes, 38. "The bus was completely gone."

The cuts come as local governments and businesses in the District, Bethesda and Arlington are promoting nightlife.

By yesterday afternoon, Metro had received 118 complaints about the short trains, an unusually high number. Some came from riders who said they had to let one or two go past before they could board.

"People are being excluded from our trains," D.C. Council member Jim Graham (D-Ward 1), who represents the District on the Metro board, said during a Metro meeting yesterday. "It's the antithesis of what we want. We're leaving them on the platforms. This was not our intention. I want a quick analysis of the seriousness of this problem."

As they debated the future of two-car trains, Metro directors also heard a progress report from Metro staff members about the prospects for operating eight-car trains.

The subway was built to operate eight-car trains, but Metro has never had enough rail cars to run trains that long. Instead, it runs a mix of four- and six-car trains during the peak periods. A crowded six-car train can handle 720 riders; an eight-car train has room for 960.

To run eight-car trains during peak hours, Metro would have to buy 120 rail cars, upgrade its power system and expand its rail yards at a cost of about $625 million.

Metro managers said recent tests delivered good news: The transit system doesn't have to install additional equipment along the tracks to make sure the longer trains stop in the right spots in the stations consistently.

Board members must decide by October whether to exercise an option on Metro's most recent rail car contract and order 50 additional subway cars. If they do, eight-car trains could run by 2006, White said.

Metro Chief Executive Richard A. White has pledged to monitor latenight crowding in subway stations.