Dayhoff Westminster: How many feet per second are traveled at 60 miles per hour?

Wednesday, June 3, 2015

How many feet per second are traveled at 60 miles per hour?

What’s an average person’s reaction time to a visual stimulus?

How many feet per second are traveled at 60 miles per hour?

Kevin E. Dayhoff

June 2, 2015: Fascinating statistic for those of us involved in emergency response – and, well, drive a car or a truck…. “What’s an average person’s reaction time to a visual stimulus? According to data collected by Human Benchmark: 0.26 seconds.” http://www.humanbenchmark.com/tests/reactiontime/statistics

I found this statistic in an article in Slate that has nothing to do with emergency response. It was an interesting article about, of all things, “Why Wasn’t Big Ben Bombed During World War II?” http://www.slate.com/blogs/quora/2015/05/25/world_war_ii_why_wasn_t_big_ben_bombed_during_the_blitz.html?wpisrc=obnetwork

The context of the statistic was about the then-“state-of-the-art Lotfernrohr 7 bombsight.”

“The bombsight has a field of vision of 35 degrees, and has a 1.4-times magnification. This would mean that you would be looking at a total area of about 115,000 square meters. Elizabeth Tower, in comparison, has a footprint of 225 square meters, occupying 0.19 percent of your total field of view. For those of you more visually inclined, it means your sight picture, once you’re right over the tower, looks something like this.

“Now, traveling at 150 kilometers per hour, you will cover the width of the tower’s footprint in a mere 0.36 seconds, or possibly slightly more than half a second if you’re coming at it on a direct diagonal.

“What’s an average person’s reaction time to a visual stimulus? According to data collected by Human Benchmark: 0.26 seconds.”

As a matter of fact, I thought that I had learned recently, in an emergency response driver’s training class; that it took the average person three-quarters of a second to react to visual stimulus.

Or put another way, how long it take you to hit the brakes after you see a problem ahead? And how many feet do you continue to travel during the time it takes you to react and hit the brakes?

Let’s look at it this way; if your reaction time is ¾ second, and you use the formula, “MPH X 1.5,” whatever that means – I’m not sure I understand my own notes… Anyway, at 40 mph you travel 60 ft per second, and if it takes you ¾ second to react, you have already traveled 45 foot towards an observed road hazard.

Perhaps we will need to consult with one of our many Westminster brainiac engineers. Jason Tyler or Mark Arnold, can you make sense out of this? Please explain.

Does it take ¼ of a second to react or ¾ of a second to react? How many feet does one travel in a car, per second, at 40 miles per hour – or 60 miles per hour?

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Photograph courtesy of “Jalonik,” “Screw miles per hour, we need feet per second,” Mike Spinelli: http://jalopnik.com/5836434/screw-miles-per-hour-we-need-feet-per-second

Measuring a car's speed by the miles it covers in an hour is as obsolete as the buffalo nickel. Drivers need a speed measurement that reflects our go-anywhere-fast lifestyle. We must replace miles per hour with feet per second. Before it's too late.

Next time you're out driving in your Plymouth Lancet or Lamborghini Inspector Rebus or whatever, look at the speedometer. What's the number read? 30 miles per hour? 40 miles per hour? 90 miles per hour? 175 miles per hour? What do those numbers even mean?

Miles-per-hour numbers have little to do with our bodies' sensory response to forward motion. As much as the inner-ear's spacial-orientation center knows, we could just as well measure a car's speed in degrees Kelvin, or microfortnights or Hoppus feet.

Related: To explore the rest of London, check out the full interactive site.

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