Distance at stoplight

Posted: Sun Aug 20, 2006 11:31 am

Once I was chatting to my neighbor. Among other things, she mentioned, that when she attended defensive driving course, they were teaching about proper distance between cars at a stoplight. They taught to stop so, that you can fully see rear wheels of the car in front of you.

The reasoning under this was, that if your car gets hit in the back, it does not hit the car in front of it at that distance. Well, this does not sound very true for me. I have at least two problems with this approach. First, it is not uniform. Imagine, what distance you should keep if you drive, say, Silverado. And now imagine you drive Honda Civic. I would think we are talking about times, not percentage difference here.

Second, it is excessive. Even with Civic we are talking about something like 10 feet, if you sit properly. Did you say the bigger the better? There is a downside to the bigger – long line at the stoplight. Sometimes it does not matter, but pretty often it does, especially for turn lanes and for intersections like this:

This intersection I’m passing every day. Route 123, which is going west - east, is a major road here, and when stoplight at the arrow 1 turns green to let the pictured cars cross the major road, stoplight at the arrow 2 turns red. It allows only the cars, which are in between the lights, to cross the road. During rush hour one can spend 5 to 10 minutes here, waiting through several stoplight cycles.

Following this rule on such an intersection is a disaster to other drivers. And most of the drivers do understand, that by stopping at the big distance, they are wasting the space that could have been used by fellow drivers behind them to save a couple of minutes (duration of stoplight cycle) on the way home.