They have those in San Francisco, one Friday afternoon a month. I've seen them, thousands of them take over Market Street, the main artery to downtown, and yet even the Police even stand by and let them run amok. They are contemptuous of cars, trucks, buses streetcars and pedestrians (I was once mowed down by one racing on the sidewalk)
It's routine to see them go flying through red lights, anything so as not to lose momentum, the ones who DO stop will go in circles so as not to put their foot down
Once I was stopped in my car on Market Street, first in line, waiting for a chance to make a right turn on red (permitted when safe to do) When I was turning the corner, all of a sudden from nowhere, a bicyclist came flying down the sidewalk, and tried to stop quick because my car was there, the last thing I saw of him was the rear of the bike in the air and the cyclist flying over the handlebars
Despite the traffic lanes they have for them, it's still pretty dangerous - the bike messengers get "doored", there've been cases when one pulled in front of a Muni bus, or a garbage truck and gotten killed that I remember, and it makes more sense to walk or ride the bus. The city traffic can be fast and unforgiving.
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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...
1995 E 420, 170k "The Red Plum" (sold)
2015 BMW 535i xdrive awd
Stage 1 DINAN, 6k, <----364 hp
1967 Mercury Cougar, 49k
2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive
(sold)