Ever since the introduction of the Bombardier cars on Caltrain in 2002, these cars have a rough relationship with bicyclists. Although Bombardiers are a huge improvement over the gallery trains with low floor boarding and two doors per side, a Bombardier bike car can only accommodate 16 bikes, versus 32 on the older gallery bike car.
On one of my recent trips on a Bombardier train, bicyclists are boarding in Mountain View:
As you can see, the current method of stacking bike together can be a source of bike congestion.
In an attempt to speed boarding, Caltrain recently designated one of the Bombardier doors as the bike entrance and the other as exit by trying to establish a flow. On that same trip at Palo Alto, bicyclists basically ignore the “exit only” sign: