I use both left and right rearview mirrors, in my case Take-a-Look eyeglass mounted ones. I got the idea from a cycling companion who used only a right hand mirror. The additional right hand mirror affords a pretty good rearward view, but is particularly useful:
- Riding on the left-hand side of a one-way street
- Riding in the middle or left lanes of a two-way thoroughfare
- In a rotary
- On a curved road to the right
- When passing entrance/exit ramps from a freeway, with the right hand mirror, I can view the ramps to my right, and stay wide of them, while watching upcoming traffic on my left, all while almost continuously looking straight ahead
- When the sun is directly behind, usually one mirror can be positioned away from the glare of the sun. As a corollary, this morning (2/5/18) at about 7:30 to 7:45 AM on mysouthbound commute, the bright, low-lying Winter morning sun was directly at the level of my left hand rearview mirror, and the sun glare made it difficult to get a fix on that mirror. My right hand, west side mirror was free of glare, with a good rearward view.
That was auspicious because on my otherwise straight 14-mile southbound ride, during that interval I had to proceed from the right side of the road to make three left hand turns,and on two occasions I was closely followed by trucks. ADDENDUM: On a northbound ride at 6:30 AM July 28, the glare of the low sun similarly obstructed my right hand mirror.
- When wearing a backpack, usually one mirror has a less-obstructed view over my shoulder.
My main argument for a mirror, particularly in the urban environment is summarized by Jim’s Law of the Road:
“No matter how well paved or lightly-traveled the Road, a vehicle is likely to pass you on the left as you encounter an obstacle on the right.”
Originally Posted by
zacster
… I can also HEAR what's coming at me, with 2 exceptions.
#1 and the most usual suspect is another bike.
#2 is an electric bus or car…
One other situation where hearing is ineffective, even on rural roads, occurs when being passed by one car, and I'm never sure that another one is following the first. No problem with a mirror.
Addendum: This past weekend I rode with a companion on a low-riding recumbent three-wheel trike. I just deflected my right-hand mirror slightly downwards so I didn’t have to crane my neck upwards to see him. The left-hand mirror was still in place to monitor reaward traffic.