There are some legal minimum following distances for heavy vehicles as well as some recommended minimum following distances. The following distance contributes to the crash avoidance space that gives a driver plenty of time to stop or take other action should something happen ahead.
Response time is the time taken to take action and it is usually between two and three seconds. That means that from when the incident unfolds ahead of you to when you actually hit the brake can be up to three seconds. In a heavy vehicle, braking is often the only option as swerving can cause rollovers with a worse outcome. Drivers should do rollover prevention training to understand the risks related to evasive manouevres.
This is why the minimum following distance when following a car or motorbike is four seconds. To calculate this, pick a point that the vehicle in front has just passed and count one
thousand and one, one thousand and two, one thousand and three, one thousand and four’
Legal minimum following distances
A road train following a long vehicle (a vehicle 7.5m or longer) must maintain a minimum following distance of 200m.
A regular long vehicle travelling behind another long vehicle must travel a minimum of 60m behind.
However, these distances do not apply on multilane roads, in built-up areas or when overtaking, and local laws can override them.
As 200m is difficult to judge, drivers can count seconds at a particular speed. At 70km/h, the distance travelled per second is 19.44. Drivers can count 10 seconds at 70km/h and approximately judge the 200m distance.
Darren is an expert on driving and transport, and is a member of the Institute of Advanced Motorists
