Stopping distances for cars

REMEMBER THE GOLDEN RULE: 

Only a fool breaks the 2 second rule.

"take a fixed point ahead (lampost, sign,bollard etc..) when the vehicle in front passes this point start counting to 2 seconds.You should reach the fixed point before your 2 seconds have lapsed"

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             Many drivers have a false belief that if the vehicle in front starts braking they can react, brake and come to a stop while still leaving the same distance between the two vehicles.

 

The total stopping distance of your vehicle depends on four things:

a) your perception time,

b) your reaction time,

c) your vehicle reaction time,

d) your vehicle's braking ability, 

 

 

 

a) Your perception time is how long you take to see a hazard and your brain realising that it is a hazard thus requiring you to take immediate action. This can be as long as 1/4 to 1/2 of a second.

 

b) Your reaction time is how long you take to move your foot from the accelerator to the brake pedal once your brain understands you are in danger. Your reaction time can vary from 1/4 to 3/4 of a second.

 

 

The first 2 components of stopping distance are down to the driver and can be affected by alcohol, drugs, tiredness, fatigue or lack of concentration. 

A perception and reaction time of 4 seconds at 100 km/h means the car travels 110 metres before the brakes are applied (this is more than the length of a football pitch!).

 

 

c) Once the brake pedal is applied it will take time for your vehicle to react. This depends on the condition your vehicle is in and, in particular, the condition of the braking system.

 

 

d) The last factor that determines your total stopping distance is the vehicle's braking capability. This depends on many things, for example:

 

*    Condition of your brakes,

*    Tyre pressure, tread and grip,

*    The weight of the vehicle,

*    The vehicle's suspension,  

*    Condition of the road surface.

*    Condition of the driver.

 

Stopping distances under dry conditions (measured in Metres)

Speed (km/h)           Reaction distance (m)    Braking distance (m)      Total stoppingg distance (m)

     30km/h                     5.5                                          5.3                                       10.8

     50km/h                     9.2                                         14.8                                      24.0

     60km/h                    11.0                                        21.4                                      32.4

     80km/h                    14.7                                        38.0                                      52.7

    100km/h                   18.3                                        59.4                                      77.7

    120km/h                   22                                           85.5                                    107.5

 

 

Stopping distances under wet conditions (measured in Metres)

Speed (km/h)          Reaction distance (m)    Braking distance (m)    Total stoppingg distance (m)

   30km/h                               5.5                                       9.4                                        14.9

   50km/h                               9.2                                     26.1                                        35.2

   60km/h                              11.0                                    37.5                                        48.5

   80km/h                              14.7                                    66.7                                         81.4

 100km/h                              18.3                                  104.3                                       122.6

 120km/h                              22                                     150.2                                       172.2

 

 

If we take a random speed, lets say 60km/h and compare it with stopping in dry conditions and stopping in wet conditions. At 60 km/h in dry conditions you will not stop the car until it has travelled 32.4 metres. 

Thats 105 feet or 2.5 Forty Foot Trucks or 3 single decker buses. 

 

In wet weather it's 48.5 mtrs until you stop. This equates to 157.5 feet or 4 x  Forty Foot Trucks.

You should walk this distance to give you a sense of how long it actually is. 

 

Remember a 5km/h difference in your speed could be the difference between life and death for a vulnerable road user like a pedestrian.

 

Hit by a car at 60km/h, 9 out of 10 pedestrians will be killed.

Hit by a car at 50km/h, 5 out of 10 of pedestrians will be killed.

Hit by a car at 30km/h, 1 out of 10 pedestrians will be killed.