If you live in an upper middle class or an even more exclusive area, you probably have neighbors who have a Toyota Prius or other types of hybrid automobiles. Most people know that these vehicles can run entirely on battery power under certain conditions, and in that situation, are extremely quiet.

An article in yesterday's Wall Street Journal entitled Blind Pedestrians Say Quiet Hybrids Pose Safety Threat got me thinking about my own safety when riding my road bike in this area. How am I supposed to know that a hybrid isn't overtaking me on a two-lane road if it's running on battery?

According to the article in The Wall Street Journal, the noise level of a Toyota Prius when accelerating under electric power is 53 decibels, while a conversation at home is about 50, and an operating vacuum cleaner is 70. If there's a cross or a head wind while I'm riding, it often limits my ability to hear vehicles behind me anyway. Think of the difficulty of hearing a hybrid approaching from behind you in those conditions.

Since people without subscriptions to the Journal will have difficulty reading this story, I'll quote the real-life scenario that begins the article, so you can see the real threat that is posed to blind people:

... Michael Osborn, a blind marketing consultant from Laguna Beach, Calif., and his guide dog, Hastings, were in the middle of an intersection one morning last April when the yellow Lab stopped short. Mr. Osborn took the cue and halted -- just in time to feel the breeze from a car passing right in front of them.

"Half an inch and it would have hit us ... it wasn't making any noise," says Mr. Osborn, 50, who has been blind for 12 years. Witnesses say the car was a Toyota Prius, a hybrid vehicle....

My conclusion after reading this article and thinking about the implications for cyclists, runners and in-line skaters wearing their iPods, and for children playing near residential streets, is that the auto manufacturing and insurance industries and public safety agencies need to study the points made by the advocacy organizations representing blind people. I think they are on to something that will be a bigger concern to the general public in the future.

If you are a cyclist, are you concerned about hybrid vehicles passing you when you are riding alone? How are you protecting yourself? Does this concern affect group rides as well? [ Subscription usually required to read articles in The Wall Street Journal ]