It is possible that I know more about riding in Chicago cabs than any human being now alive. Okay, maybe not, but I have logged serious, serious time in cabs, pushed many bills through the Plexiglass barriers, and can note therefore with some confidence:
The Very Most Annoying Thing That Cab Drivers Do
The Creep (AKA Taxi Creep, Cap Creep) is a function of a cab driver's (complete) inability to come to a complete stop--an inability to bring the vehicle to rest. Cab drivers spend all day--weeks, years--whizzing around the city, sliding through yellow lights, making rolling stops, getting through traffic as fast as they can (most of them, anyway), and eventually some drivers--or actually maybe the ones who do this have always done so, because they seem really attached to this behavior--just can't stop, period. They can't stop not stopping.
What happens during the Creep is that the cab will brake to a red light, but immediately take his foot of the brake and periodically pump it, so that the 60 seconds that you're at the light comprises a series of little herky-jerky lurches as you get farther and farther out through the crosswalks and beyond. I've been in cabs that were halfway through an intersection already when the light turns green. Creepers just can't sit there. They can usually manage about three seconds of Still, before they--unconsciously, I think--are in motion again with another pump. And another and another.
It's not just the slow creep into pedestrian traffic and intersections that is annoying, it's the feeling it creates. You can feel the (unconscious, but) building impatience from the driver's foot, through the cab, into your own body. You want to tell the dude (I've had about three female cab drivers in 20 years) to just stop. Stop! You can't make it go any faster, you aren't exempt from the normal rules of traffic, I'm tired of my body being hiccuped forward in tiny little lurches over and over. Please stop! (A parallel phenomenon, by the way, is the driver who does the same with the gas pedal--pumps the gas over and over, so that time on the open road is a series of accelerations rather than smooth rolling. It's just as annnoying. Please Go!)
There is absolutely nothing to do about the Creep, by the way. I do often make an involuntary gesture of putting my hand up on the seat in front of me to try to "stop" it--involuntary, inevitable, probably passive-aggressive in origin--but that does nothing. All I can do is note it.