Monday, November 3, 2008

Seeing red

Most major streets in greater Louisville meet at intersections controlled by traffic signals  ("signalized intersections" in traffic engineering lingo). In spite of the number and severity of crashes at signalized intersections, the inconvenience of stopping at red lights regardless of traffic volumes, and the high cost of building and maintaining these intersections, I took them for granted until recently. It seemed as though they must improve traffic flow and safety compared to other options (stop signs, for example) or else the traffic engineers would stop using them. I certainly don't want a more chaotic traffic environment than we have now.

As regular readers know, I prefer modern roundabouts (not traffic circles) to signalized intersections in many situations. I believe that one-lane roundabouts could replace many of the traffic signals in our area with benefits for motorists, bicyclists, and pedestrians. Of course, a transition from signalized intersections to roundabouts would cost money and involve controversy. Even in the best-case scenario, we will have lots of traffic signals for years to come.

As long as we use traffic signals, we need to make them functional for all legal road users. In Louisville, we have two basic types of traffic signals: signals timed to turn from red to green on a fixed schedule, which might differ for different times of day (for example, morning rush hour versus evening rush hour); and signals that stay green for traffic along the more major street until a sensor detects vehicles waiting on the smaller street. I'll call the first type "timed signals" and the second type "sensor signals." Locally, very few signals of either type work well for bicyclists. Tomorrow, I'll explain the problems and explore solutions. 

1 comment:

john said...

I'm a big fan of roundabouts as well. With the proper selection of sites for them, I do believe they would be accepted by most users.

However, living near the school for the blind, the concern that sticks in my mind is how visually- and mobility-impaired pedestrians would cross safely. As I recall from traffic engineering courses, this concern has been raised in other communities and there has been some research on the subject. Do you know what is being done to address this?