Originally Posted by bakerjw

You ought to see my afternoon commute. 1/2 mile downhill to a stop light one of the busier intersections in the area. The best scenario is if it is red and I am 3 or 4 cars behind the lead car. Once it turns red, I can maintain speed with the traffic for a couple of other lights until the road widens and there is a bike lane. FWIW the bike lane is covered with road debris.

It is a little unnerving to be in the mix of traffic like that but unless I get some rammy driver behind me who just can't stand being behind a cyclist, all is well.

I would say that fear is as dangerous as complacency.

Originally Posted by Jim from Boston

… IMO, besides routine monitoring rearwards with the mirror, a most important use is to make quick decisions when encountering an obstacle in front of you, such as a car door, pothole, car entering your path, etc. Can you immediately veer left?...

Personally, I use an eyeglass mounted Take-a-Look mirror that allows me to maintain a forward-looking head position with just a sideward glance to see the rear.

I really don’t want to turn my head for an over shoulder glance away from the line of travel when speeding downhill on a pothole-strewn road with heavy traffic to my left and parked cars to my right. Furthermore, wind noise can sometimes obscure the sound of a passing car.

I find mirrors so easy to use, and so helpful that I wear both right and left (link).