Re: Motorcyclists. Years ago when I commuted across the SF Bay Bridge everyday it was bumper to bumper stop and go traffic at intervals interspersed with periods of near bumper to bumper speeds of 30-40 mpg. Everyday I would see motorcyclists try an zip though traffic between lanes at speeds 10-20 mph in excess of prevailing speeds. It was no big deal when traffic was at the stop and go pace, but very dangerous during the intervals of higher speed. Some drivers in cars just cannot resist trying to move a small amount ahead in traffic by switching lines at every opportunity at those higher speed intervals. It is very difficult to even see a motorcycle coming up between lanes, especially when the driver is concentrating on checking for a car in the other lane. I observed a few motorcyclists get taken out this way. It was never clear to me what traffic regulations were regarding that; that is motorcyclists driving between lanes.