BART passengers may notice some changes during their commute to work this week. The transportation service began running on an expanded schedule and operating with longer train cars during rush hour on Monday.

“The schedule change is there to reflect not only the way people are commuting, but also reflect the changing population of the Bay Area,” said Taylor Huckaby, a BART communications officer, saying the agency wants to expand service as the population grows. Officials began analyzing people’s commuting patterns months ago, he said, and found that there has been an increase of the number of passengers who start their commute later in the morning.

To accommodate passengers who are starting to commute later, trains running during rush hour on the Dublin/Pleasanton-Daly City Line, Fremont-Daly City Line and Pittsburg/Bay Point Line will now run for an additional 15 minutes.

BART officials also lengthened the number of cars on transbay routes during rush hour and eliminated the three-car train from the service. Richmond-Fremont, the last route to run a three-car train, now runs a four-car train during non-commute hours. BART maintenance workers will work more shifts to put more cars on the tracks, Huckaby said.

Rush hour times are 5 a.m. to 9:45 a.m. and 4 p.m. to 7:30 p.m.

Officials also lengthened the hours of operation on some routes. The Richmond-Millbrae Line now runs an additional hour on weekday evenings until 9 p.m., and the BART to Oakland International Airport trains run every six minutes until 11 p.m. From then, it runs every 20 minutes.

There is also a new service line. Some of the six morning “reverse commute” trains that start at Montgomery station in San Francisco became the Pleasant Hill/Limited Line. This line stops at Pleasant Hill and bypasses the Rockridge, Orinda and Lafayette stations. Officials warn passengers who want to get off at either of those stations to pay close attention to the platform and not board the line that says “Pleasant Hill/Limited.”

Also on the Pittsburg/Bay Point Line, the rush hour trains that run to Concord, Montgomery or Daly City in the morning and Concord, 24th Street or Daly City in the afternoon will no longer turn back to San Francisco on Concord. Instead, the trains will turn back on Pleasant Hill.

The service changes are aimed at relieving crowds and molding the service to commuters’ traveling patterns before new train cars arrive fall 2016, Huckaby said. “People are packed on there like sardines,” he said. “Public transit has been so successful that people have crammed on.”

One of the most crowded BART stops is 19th Street in uptown Oakland, where there has been an increase of population due to a booming residential market, Huckaby said.

Commuters at 19th Street station said they were happy to hear of the extension. “I don’t know what the reason for the three-car train would be,” said Stefanie Corrales, who was waiting for the train to Pleasant Hill during evening rush hour. “It’s like the penny.”

Sandy Rosen commutes on the Pittsburg/Bay Point line from Lafayette to 19th Street in downtown Oakland. “I wish I wasn’t in Lafayette so I could take advantage” of the new changes, she said.

On Tuesday, some passengers had already noticed some changes in their commute. Rosen, who has commuted for ten years, said she noticed her morning ride was less crowded.

Others, however, have yet to see any changes. Carri Earl, who was waiting for the train to Concord at 19th Street, said her early commute to the station from Concord was bad. “People were standing in the aisles at that point, so it was more crowded than I was used to seeing it,” she said.