News has hit the headlines today that the 20 KPH speed buffer is being removed on many major roads and highways in Abu Dhabi.

It is right that motorists should be clear about the speed they are permitted to drive and the existing buffer has, effectively, caused great confusion and disparity between vehicles travelling at the published speed limit, and those that exceed it by the permitted margin.

However, to remove a speed buffer entirely is, in my opinion, inadvisable for a number of reasons.

1) Even with the speed buffer in place, it is very easy to incur a fine for travelling 1 KPH over the maximum permitted speed. For example a car travelling in a 120 KPH zone is permitted to drive up to 140 KPH and will receive a fine if caught travelling at 141 KPH.

This practice encourages drivers (especially those without a cruise control) to fixate their attention on the speedometer to ensure they remain at the target speed they have selected. This is an unsafe practice which diverts their attention from the road conditions.

International best practice for the enforcement of speed limits, assumes a safe margin for error for the following reasons:

a) When entering a lower speed limit from a higher speed limit, the driver requires i) reaction time to adjust their speed and then ii) time for the vehicle to decelerate to the new speed.
b) When overtaking a slower vehicle which may be travelling a few KPH below the published speed limit, a faster vehicle should accelerate and complete the manoeuvre as quickly as possible.
c) When taking avoiding action, acceleration is sometimes preferable to braking, especially if the driver is aware of being tailgated by another vehicle who is travelling too close.

In each case, this may take the vehicle a few KPH over the published speed for a limited distance. In the case of b) it would be more hazardous for a vehicle to overtake a slower vehicle at the published speed limit, due to the excessive distance such a manoeuvre would take to complete. This is especially true on so-called “truck roads”. In the case of c) braking may precipitate a rear-end collision.

d) Speed enforcement cameras must be calibrated accurately in order to stand up as evidence in court. The construction file and calibration routines must be traceable and shown to be accurate to within a certain tolerance above the speed limit. It is not acceptable to enforce fines for vehicles travelling at or below the speed limit, and therefore there must be a technical buffer provided above the speed limit to ensure adequate proof that the vehicle was in fact speeding.

International road safety statistics suggest that excessive speed, whilst it may be a contributing factor, is not the prime cause of accidents. The prime cause of accidents is poor driving which results from distraction, or poor judgement and anticipation.

To cause drivers to fixate on their speedometer, is a prime source of distraction which will not improve road safety. It will also cause more drivers to be unfairly penalised for safe driving practices.

Therefore I recommend that while the 20KPH buffer is reduced, a smaller buffer may be provided that allows for a safe margin for error. In the UK, the ACPO Speed Enforcement Policy Guidelines are 10% +2mph (approximately 10% + 3 KPH). Therefore in a 60 KPH zone, the vehicle would be permitted 69 KPH and a fine triggered at 70KPH. In a 120 KPH zone, the vehicle would be permitted 135 KPH and a fine triggered at 136KPH.

The purpose of using a percentage is so that drivers primarily use the published speed limit as their target speed but are not penalised unfairly for normal and safe driving practice. This means they can keep their attention outside the vehicle and rely on their judgement of speed within the flow of normal traffic, rather than fixating on the speedometer.


Andy Woolford