Professional Driver's Handbook

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Danger zones

The danger zone of any vehicle can be described as the area directly in front of the vehicle in which the vehicle cannot stop. In the following diagram, the danger zone is shown as the shaded area. As the speed increases, the danger zone increases; if the road condition is less than ideal because of rain, snow, ice or gravel, the danger zone is increased. When you fail to reduce your vehicle’s speed to suit these road conditions, the danger zone increases.

At 30 km/h you can stop - just!

The truck is approximately three and one-half car lengths from the crosswalk when the driver sees the pedestrian. Under ideal conditions, the driver may be able to stop just in time.

Danger Zone


At 50 km/h you cannot stop in time!

Even under ideal conditions, the driver of the truck cannot stop in time!

Both the pedestrian and the car on the right are about to enter the danger zone!

The distances in the diagrams are approximations only for illustration, as braking distances will vary according to the weight of the vehicle, condition of the brakes and the condition of the road surface.

When conditions are less than ideal, commercial vehicles, like passenger vehicles, can decrease their stopping distance by reducing their speed.

If another vehicle or a pedestrian should enter the danger zone, the driver cannot stop the vehicle in time. It is not physically possible.

Danger Zone 2


Shrinking the danger zone

The illustration of the danger zones shows how the distance is shortened if the speed of the vehicle is reduced.


The zone can also be reduced if you form the habit of "covering the brake" when you recognize potential danger developing. In the previous diagram, the driver has recognized that he/she is nearing an intersection which is a danger spot. The driver knows the line of cars on the right may hide hazards from view. The driver removes his/her foot from the accelerator and places it lightly on the brake. When the driver first sees the hazard, the reaction time has been reduced because the driverremoved his/her foot from the accelerator. Therefore, the stopping distance has been reduced and he/she now has a better chance of stopping before the crosswalk, rather than across the intersection.

Speed, weight and stopping

If the vehicle's:Then to stop, you need:
weight is doubleddouble the braking force
speed is doubledfour times the braking force
weight AND speed are doubledeight times the braking force


Rev: 2017