Andrew Rudin – March 1994
Comfort and Light Newsletter #53
Philadelphia drivers have two driving habits that work at cross-purposes — jump starting red lights as they turn green and running the yellow ones before they turn red. The City Department of Streets had an idea to increase safety and save energy costs at the same time — replace the traffic lights with all-way stop signs at moderate traffic intersections.
In the 1960s, Philadelphia citizens were demanding stop lights. From 1964 to 1966, the Department of Streets installed 370 signals. They noticed, however, that pedestrian injuries increased 30%, occupant injuries increased 46% and traffic fatalities increased 23%
In 1978, the Department of Streets began their program to remove electric traffic lights. Over the next ten years, they replaced 426 signals with all-way stop signs. A study of 235 of those intersections compared the accident rates three years before replacement and three years after replacement.
Here are the results:
Type of accident Decline
Pedestrian injury 42%
Vehicle occupant injury 47%
Property damage only 60%
Right-angle accidents 60%
Rear-end accidents 52%
Twenty-five of the removals were at school crossings where there likely was no guard assigned. For calendar year 1990, there were two accidents at these intersections and neither occurred during school hours or involved school children.
Eight hundred additional removals are planned, which will increase safety and reduce energy and maintenance costs.
What can we learn from this?
First, at intersections without an electric signal light, we are apt to slow down more. More importantly, we are better at depending on visual signals from each other than from signals from an electric light.