Page 35 - Driving Commercial Vehicles Manual

driving commercial vehicles

Speed and weight facts
fast fact
Speed and weight affect the stopping power required to stop any vehicle, and
Driving without due care and how far it will travel before it stops. You need more stopping power whenever
attention and unsafe speed the speed you’re travelling and/or the weight of your vehicle increases:
are the top two factors
assigned to commercial • 2 ✕ vehicle speed requires 4 ✕ the stopping power
drivers involved in police- • 2 ✕ vehicle weight requires 2 ✕ the stopping power
reported casualty crashes.
Traffic Collision Statistics: • 2 ✕ vehicle speed and 2 ✕ vehicle weight requires 8 ✕ the stopping power.
British Columbia (2007)
Stopping power required to stop a vehicle

Speed unchanged — weight doubled Weight unchanged — speed doubled

10,000kg 30 km/h 10,000kg 30 km/h

20,000kg 30 km/h 10,000kg 60 km/h
2 X vehicle weight requires 2 X the stopping power 2 X vehicle speed requires 4 X the stopping power

Both weight and speed doubled

20,000kg 60 km/h
2 X vehicle weight + 2 X vehicle speed requires 8 X the stopping power

A typical compact car weighs about 1,000 kg. The truck in the illustration
above may weigh 25,000 kg when fully loaded — over 25 times heavier than
a car. And heavy tractor-trailer combinations can weigh up to 63,500 kg.
There’s only so much stopping power available, and the faster the vehicle is
travelling, the more power it needs to stop. This is why it’s so important to
drive at a safe speed, at a safe following distance, and within the vehicle’s
stopping capability.
Compared to cars, trucks and buses have larger brake components, more
wheels and more brake linings/shoes or rotors/pads. But trucks and buses
have longer stopping distances.

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