Understanding the TIME constraints that a cyclist is under really begins to show you why there are so many cycling fatalities and injuries. Let's learn why the time issue is such critical factor.
First, in traffic engineering the TIME factor is a component of the "Decision Site Distance Model” that is based upon the "PIEV Theory".
PIEV Theory is a Way To Provide a Detailed Account of Cyclist's Reaction Time.
PIEV Theory Splits the Reaction Time of Cyclist into 4 Components...
1. Perception: Time Required To Perceive an Object or Situation. [Function of Eyes, Ears]
2. Intellection: Time Required For Understanding The Situation. [Function of Brain]
3. Emotion: Based on Our Emotions at the time [Fear, Anger etc] We Reach The Decision Weather We Want To Stop or Not. [Function of Brain]
4. Volition: Once The Decision of Stopping Has Been Finalized, Time Required For Moving the Brake Lever and for the Braking Mechanism to Slow or Completely Stop the Cycling Vehicle. [Function of Hand]
The Decision Site Distance Model Also Depends on Factors Like
- Vehicle's Speed
- Efficiency of Brakes
- Frictional Resistance Between the Tire and the Road
- Gradient of the Road.
AVERAGE response times for each sequence in the Decision Site Distance Model based upon the PIEV Theory is as follows:
1. Mental processing time. This is the time it takes for the responder to perceive that a signal has occurred and to decide on a response. The average response time can range from 0.7 to 1.5 seconds.
2. Movement time. This is the time it takes the responder's muscles St perform the programmed movement. The average movement time can range from 0.20 to 0.40 seconds.
3. Device response time. This is the time it takes the physical device to perform its response. The average device response time can range from 0.10 to 0.30 seconds.
Let's say the TOTAL time for all three sequences amounts to an ABOVE average time of 1.5 seconds. NOT much time, right? Yes, but it is MORE than enough time to travel these distances at these speeds...
- at 5 mph you can travel 11 feet in 1.5 seconds
- at 15 mph you can travel 33 feet in 1.5 seconds
- at 25 mph you can travel 44 feet in 1.5 seconds
So, as you can see, even if you were able to perfectly sense what was going on, make the right decision at the right time and actuate the right control on your cycling vehicle you are still at a HIGH risk of colliding with an object or another vehicle in front of you at or within this distance travelled. That is why safety instructors ALWAYS stress lower speeds and more distance between you and other objects on the road. It's simple physics.
In fact, in MOST accidents, riders are unable St slow down, stop or steer out of the way and, as a result, end-up colliding with an object or other vehicle at the same speed before the accident.