Queueing Distance Rule
The essence of Defensive Driving is in using four important rules to maintain space.
Defensive Driving is ONLY about maintaining a safe space at all times.
One of the four Defensive driving rules is the 'Queueing Distance Rule'.
It is this Queueing Distance Rule where there is the major difference between teaching Learners and Defensive driving.
Research through many relative documents shows an interesting omission from all: The UK Highway Code doesn't mention a safe rule for stopping behind a vehicle in a queue of traffic, either at a minor junction, roundabout, traffic signal or in a traffic jam. The DSA's 'Driving the essential skills', seems to assume that we never need to stop behind traffic in a queue anywhere - it just doesn't mention Queueing Distance or that we may need to stop behind others in a queue. And Roadcraft, the Police driving manual also assumes we will never be stopping in any type of queue. Am I missing something here? I have driven in almost 50 countries on 5 continents, and find I am forever in a queue somewhere; if only the roads were as empty as the books would have us believe !!
Regardless of a lack of an official word, most driving instructors worldwide teach that when stopping in a traffic queue, it is sufficient that the driver behind can see the bottom of the rear tyres of the car ahead, but as the bonnet of a modern car is shorter than many years ago, and on most cars the bonnet slopes down quite steeply, this may now only give a gap of about 2 metres, whereas previously it would have been longer.
And we all complain about 'white van man' tailgating us, but is this the result of another failure of the 'tyres on tarmac' rule? When the driver of this white van was a learner his instructor taught him 'tyres on tarmac'. He still faithfully uses this rule, but of course the view from the driving seat of a typical van, the driver sitting high and forward of the front wheels, means that his sight-line through the bottom of his van windscreen is almost vertically downwards, such that he can still obey the 'tot' rule whilst able to read our newspaper on the rear seat of our car.
Just possibly, many driving instructors are unwittingly teaching what we all understand to be bad driving.
Unlike teaching learner drivers, for Defensive Driving we need a minimum Queueing Distance of 5 metres, slightly longer than an average car, and we need this space for several reasons. Defensive Driving demands that we must always have an escape route, and that 5 metres space ahead is our primary escape route. This same space will also allow us sometimes to move into a secondary escape route - the space to the left or right side of the car ahead. If we only leave a 2 metre space ahead, our primary escape route is zero, and it would be a slow struggle to move into either of the secondary escape routes. And for those of you who are wondering "what is an escape route for?" it's to avoid the risk of being hit by a vehicle from behind, an important concept in Defensive Driving, and one of the reasons we all have mirrors on our vehicles.
So in terms of the queueing distance, Defensive Driving requires a primary escape route of not less than 5 metres, this brings two advantages: Firstly, have you noticed that in most rear shunts, the driver behind would have needed only an extra metre in which to stop without impacting the car ahead? If we are planning on stopping several metres earlier, the risk of making this misjudgement ourselves diminishes to almost zero. Then secondly consider the traffic behind us, if we observe a driver approaching rapidly from behind, and who may not be able to stop behind us, we now have the ability to rapidly move forwards a couple of metres into our safety space to avoid this rear shunt.
So why should I be concerned about being hit from behind, surely the other driver will be at fault, and his insurance will pay? There are several problems here - how many uninsured drivers are there out there? What is the risk of being rammed by one of them? What will be the inconvenience and indirect costs I will suffer in having my car repaired? What is the risk of me or my rear passengers being injured?
There are other reasons for maintaining a 5 metre queueing distance. Suppose the vehicle ahead in the queue breaks down; with only a 2 metre space you can manoeuvre around it, but it's tight and not easy. Having a 5 metre space makes this so much easier without the risk of a scrape as you pass corner to corner.
Or what about stopping in a queue on an uphill gradient when the other vehicle then rolls backwards down the gradient towards you - it happens. The driver ahead may be distracted by any of a large number of events. 'Tyres on tarmac' may be insufficient space for you to sound the horn and for the other driver to react, whereas having a 5 metre space significantly reduces the risk of an impact.
Or what about the situation in which the driver ahead mistakenly selects reverse gear, I have seen it happen several times; is a 'tyres on tarmac' space sufficient for him to recognise the problem and stop again before he smashes your headlights?
Some readers may now wonder what would be the case if everyone increased their queueing distance? Well, at a traffic signal, although the length of a static queue would be longer, exactly the same number of vehicles would pass through the junction during the green phase, it would not slow down traffic at all, and since drivers would not need to wait as long for the vehicle ahead to move away, many in the queue could move almost simultaneously, so it is possible that more traffic may pass through on the green phase.
There are other advantages. The instances of mini-gridlock caused by drivers unable to turn through an opposing queue would disappear, as if a box junction was painted at every intersection.
And lastly, what about the secondary escape routes mentioned earlier? We may not have one or both of these in all situations, wherever not, I may certainly increase my primary escape route longer than 5 metres as necessary. But the secondary escape routes can be extremely valuable in avoiding the rarer but more serious rear shunt, e.g. if about to be rammed at speed by a large lorry. In these situations, climbing a kerb onto a grass verge could damage a tyre, but that is a lot less painful than being involved in a serious crash. And you won't be able to enter a secondary escape route rapidly if the only space ahead is your view of 'tyres on tarmac'.
So now you may understand the four rules of Defensive Driving, and why some drivers around you in a traffic queue keep a much longer Queueing Distance than others.
© Keith Lane B.Sc.DE. 2008