Report examines impairment as a driving risk

Various impairment factors including alcohol, drugs, fatigue, eyesight and general health have been examined in a new report made available from PACTS.

The UK’s Parliamentary Advisory Council for Transport Safety (PACTS) has published a report entitled “Fit to Drive?”, which was written in conjunction with road safety experts. The report examines the laws governing driving impairment, the factors that influence a person’s fitness to drive and any gaps between these factors and existing legislation that need to be addressed.

The headline result of the study leading up to the report is that whilst being under the influence of alcohol is the biggest driving impairment, there is evidence that drivers are taking to the road whilst impaired but don’t realise it.

According to the lead author of the report, Professor Oliver Carsten, it is well known that behavioural factors such as using alcohol or drugs affects the fitness of a person to drive, but there are other factors which are less widely known. “There are long-term factors such as physical or cognitive impairment that account for 6% of all fatal crashes, while fatigue is a factor in 3%,” he said.

The report examined alcohol, drugs, fatigue, visual acuity and physical or mental health and provided recommendations on each type of impairment:


* Because of widespread breath-testing following crashes, alcohol may be over-attributed as the key factor
* Following Scotland’s lead by lowering the legal limit to 50mg/100ml (0.05% BAC) could save an estimated 25 lives and 95 serious injuries annually
* Higher rates of enforcement would provide more of a deterrent
* The Department for Transport (DfT) and Home Office should focus on Type Approval of roadside evidential breath testing equipment to save police time
* Fleets should follow the lead of National Express buses and install alcolocks
* Alcolocks should be used in the rehabilitation of previous drink-drive offenders

Illegal and prescribed drugs

* There is a “Zero Tolerance” approach to illicit drugs which is political rather than road safety based
* Incidence of illicit drugs in both fatal and non-fatal crashes is around 6%
* At present only 2 out of the 16 proscribed drugs have devices Type Approved for roadside detection
* The difficulty of detecting drivers under the influence of drugs at the roadside reduces the efficacy of a law
* Medicinal drugs – if taken according to prescription – represent a low risk

Fatigue and sleep impairment

* Early studies failed to identify fatigue as a risk factor because if a driver survived a fatigue related crash, they were likely to deny culpability and if they did not survive, then there was little evidence that fatigue was a cause
* It is now widely accepted that fatigue is a major contributory factor particularly in the early hours of the morning and on long distance journeys on major roads or motorways
* The Highway Code now gives specific advice on the risks of sleep deprivation, time spent driving and natural body-clock rhythms
* Highways England and other strategic road authorities should consider design treatments that can break up the monotony of long-distance driving

Uncorrected defective eyesight

* Safe driving depends more than 90% on eyesight but there is no strong evidence that deficiencies in eyesight present a major road safety risk
* Some aspects of eyesight – contrast sensitivity, visual field impairment and visual processing speed are related to risk
* Eyesight-deficient drivers tend to restrict their driving to avoid difficult times eg at night
* This is particularly likely for elderly drivers, and with an ageing population, eyesight is likely to increase as a risk factor
* Current procedures are not sufficient to identify those with inadequate eyesight

Mental or physical illness or disability

* Many medical conditions cause long-term cognitive impairment, including brain injury, Parkinson’s, dementia, multiple sclerosis and strokes
* Many of these conditions are age-related and set to increase with an ageing population in the next 20 years
* Evidence points to an increase in collision involvement rates among older drivers
* Discussing fitness to drive may be difficult for the GP who risks their relationship with the patient
* Different diseases and injuries produce different types of cognitive impairment which may impact driving ability
* There is no single set of tests to assess fitness to drive irrespective of the underlying causes of the impairment
* The Government should fund research into developing a clinically viable desk based assessment of driving safety
* If a driver is advised to stop, they need to be supported with alternatives to maintain mobility and avoid social exclusion.
* Autonomous cars may have a role to play in supporting the safer mobility of people with cognitive impairment

“The EU Directive on fitness to drive includes the requirement to consult with “authorised medical opinion” to obtain expert judgement on many of the factors,” says Professor Carsten. “However, we have to ask how that expert judgement is to be obtained and who is qualified to give it.”

David Davies, Executive Director of PACTS said: “The Government has recently published its road safety statement reaffirming its aims to reduce death and injury on the road. This report highlights where improvements are to be made and we hope that all relevant departments and agencies collaborate to act on its recommendations.”

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Human Factors

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