Know Your Stopping Distance

Know your stopping distance

Most of us feel that whenever we apply the brake, the vehicle will stop immediately. That is not the case.

We try to stop the vehicle we are driving, whenever we sight a hazard on the road, in front of us. We apply the brake immediately to bring the vehicle to a stop. Depending on the speed we were driving, the vehicle will travel some distance before it becomes still. Let us understand the implications.

Depending on our mental state, we take some time to react and apply the brake. This time is known as reaction time and by this time the vehicle had moved forward to some distance. This distance is known as reaction distance. After we apply the brake, the vehicle further travels a distance before coming to a halt. This distance is known as braking distance. So, the total distance traveled by the vehicle is the sum of reaction distance and braking distance.

Stopping distance = Reaction distance + Braking distance

The reaction distance.

The reaction distance is affected by:

1.       The speed of the vehicle

2.       Our reaction time (The normal range is 0.5 to 2.0 seconds)

People in the age group of 45 – 54 have the best reaction time. 18 – 24 group (due to their sharpness) and above 60 age group (due to their experience) have the same reaction time.

The reaction time can be reduced by:

1.       Anticipation of hazards

2.       Preparedness

The possibilities for longer reaction times are:

1.       Delay in decision making

2.       Alcohol, drug and medication

3.       Tiredness

The reaction distance can be calculated by using the formula RD = (S * R) / 3.6

Where RD is distance in metre

             S is speed in KMPH

             R is reaction time in seconds

Example: If a vehicle is driven at 60 KMPH and the reaction time is 1 sec, what will be the reaction distance.

RD = (60 * 1) / 3.6 = 16.67 metre

The braking distance.

The braking distance is affected by:

1.       The speed of the vehicle

2.       Condition of the road (wet, dry, rough, smooth)

3.       Gradient of the road

4.       Load of the vehicle

5.       The brakes (condition, technology, to how many wheels the brake is being applied)

6.       Condition of tyres

Breaking distance calculation.

It is very difficult to calculate the braking distance accurately since so many parameters are involved. Use the following formula assuming dry road, good tyres and good brake condition.

Braking distance BD = S² / 259.2 metre

Considering the same speed of 60 KMPH, the braking distance BD = (60 * 60) / 259.2 = 13.89 metre

Stopping time.

So, the total distance for the vehicle to come to a complete stop will be (16.67 + 13.89) 30.56 metre

Even if we consider the best reaction time of 0.5 second, the total distance will become 22.23 metre

The following table gives the stopping distances for speeds. Reaction time of 1 second is considered while calculating the reaction distance.

       

While driving at higher speeds, it is a safe practice to leave the required space between us and the vehicle in front. This will help us to avoid collisions.