BART, the regional rail system that is carrying more passengers on a typical weekday than ever before, has been quietly removing seats from trains to make room for even more riders.

Six seats are being removed from some cars to create more space for people to stand and to accommodate the growing number of on-board bikes and the luggage hauled by passengers heading to and from San Francisco International Airport.

"Crowding is not going to get to the point of New York or Tokyo, but we are carrying a lot more passengers, and we have to figure out how we can comfortably accommodate more people," Paul Oversier, BART's assistant general manager of operations, said Thursday.

BART carries 360,000 passengers on an average weekday, and the number is expected to grow. Agency officials, who expect to have new trains designed to handle bigger crowds by then, predict 150,000 more riders a day by 2025.

The system today has very little room to add trains, which means the agency has to figure out how to squeeze in more people - notably during the rush-hour crush.

The challenge, however, is to not get to the point at which passengers get crammed in so tightly that they opt to drive or take AC Transit or San Francisco's Municipal Railway instead.