Why No Bikes on BART Escalators?

Every time I ride BART, I’ve always noticed the sign at the bottom of the escalator that forcefully commands, “No Bikes on Escalator,” and have wondered why that is the case.  A periodic loudspeaker announcement clarifies that it’s for our own safety and that of our fellow BART riders, but this has always seemed like a cop-out to me.

I really can’t tell what’s so dangerous about holding a bike on an escalator while it’s moving upwards.  Surely, you don’t need to monopolize the whole escalator like the person above is doing; there is plenty of space to fit both you and your bicycle while also keeping an avenue open on the left side for others who want to pass.  Moreover, doesn’t it seem even more dangerous for a smallish individual to attempt to lug his or her bicycle up that daunting BART staircase?

Some quick research reveals that while some people are completely against the idea, certain situations sometimes make it a necessity.  So, how do YOU feel about bikes on escalators?  Can anyone provide a cogent reason for why this is a forbidden practice?

[Photo by tinka516]