American Scientist

To the Editors:

I returned from a monthlong trip to Central Asia to find the May–June issue with Henry Petroski’s Engineering column “Traffic Signals, Dilemma Zones, and Red-Light Cameras,” which I then read with great interest.

The discussion of the yellow light timing reminded me of the different traffic-light configuration I observed in both Ashgabat, Turkmenistan, and Baku, Azerbaijan. There, the yellow light is replaced with a countdown of the time until the light changes from green to red or from red to green, rather like the walk/wait signs for pedestrians in many places.

Whether this configuration results in more or less respect for this equivalent to the yellow light, it certainly captures and holds the attention of drivers. It would be interesting to know whether it results in fewer violations or collisions, because it eliminates the temptation to guess how long it will be before the yellow light turns red.

James Royle
San Diego, CA