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Monday, April 23, 2012

How to Remember Typical Stopping Distances in The Highway Code

The Highway Code (UK) gives the following list of typical stopping distances. The Highway Code gives no hint on the source of this information, nor it gives any insight on the method used to calculate these values. It does, however, state that "your typical stopping distance consists of thinking distance plus breaking distance."

Being a learner, it's difficult for me to understand how remembering these numbers to precise detail will help me in effectively avoiding road hazards. More so, I can't precisely tell the difference in 73 meters and 96 meters while driving at a speed of 60mph.

Unfortunate as it might be, one needs to remember all these values by heart, as part of the theory test in the UK. Here are some hints to get you going. Look at the chart in detail, and read the following hints:
  1. The speed goes from 20mph to 70mph in increments of 10 in this chart. The most important hint is that 50 mph and above are the speeds where the total stopping distances are more than the value of the speed. For speeds less than 50 mph, the total stopping distance in meters is less than the speed in mph.
  2. If you look at the thinking distance, they are in multiples of 3. If you multiply the speed by 3 and drop off a zero, you get the thinking distance. So, the thinking distance at 20 mph can be calculated as 20x3=60, which gives 6 meters when you drop a zero. Similarly, the thinking distance at 70 mph can be calculated as 70x3=210, which gives 21 meters.
  3. The breaking distance (6 meters) at 20 mph is same as the thinking distance (6 meters). The total distance is just s sum of these values: 12 meters.
  4. An average car length, according to this chart, is 4 meters. The total stopping distance for 20 mph is 3 cars (equals to 12 meters). The stopping distances go like this: 3 cars, 3 more cars, 3 more cars, 4 more cards, 5 more cars and finally 6 cars. In this way, the total stopping distance at 70 mph is 24 cars, which gives 24 cars x 4 meters each = 96 meters.

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