Brake Reaction Time

In the mid 1930s, Dr. Harry DeSilva of the Massachusetts State College at Amherst created a brake reaction test to measure how quickly drivers can step on the brake in response to a red light. He took it around the country and tested thousands of people.

People in their mid 20s generally had the quickest reaction times, and then times declined with age, which wasn't a surprise. Slightly more surprising was that short people generally had faster responses than tall people. From Time magazine (Aug 1935):

The average reaction time was .43 sec. The fastest was .26 sec. The slowest was .90 sec. It was found that tall persons generally react a little more slowly than short people, no doubt because motor nerve impulses travel through the body at about 300 ft. per sec. and thus for tall persons the motor impulse would take longer to go from the brain to the foot. Another theory is that short people simply have less leg to deal with.

Time - Aug 26, 1935

Democrat and Chronicle - Mar 15, 1936

     Posted By: Alex - Fri Mar 17, 2017
     Category: Motor Vehicles | Cars | Psychology | 1930s

Sounds about right. Reaction time to visual stimuli is generally around 300 ms.
Posted by RobK on 03/17/17 at 10:30 AM
Makes sense why I go through so many red lights:

The odds are so stacked against me that it's safest if I don't even bother slowing!
Posted by Jessica on 03/17/17 at 12:28 PM
Too bad that modern autos coddle the driver. Jay Leno made an observation about old cars where there was no padding on the dashboard and no seat restraints: "After a wreck, you just hose off the dash and sell it to the next guy."
Posted by KDP on 03/17/17 at 03:25 PM
I took one of these tests when I was about 14. (No, that wasn't in the mid 30's. Ha ha.) I remember that my time raised the tester's eyebrows, so I must have been close to that 0.26 sec. mark. Surely, my time has been rising ever since then. However, now that I have a car with an automatic "transmixer," I use my left foot for the brake. I'll bet that's gotten some reaction time back.
Posted by Virtual on 03/18/17 at 12:05 AM
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