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Stricter vision function tests for drivers can reduce accidents, says study

India ranks lowest in terms of road safety. There is a need to scientifically analyse the factors causing road accidents and come up with guidelines to take corrective actions. Prof. Ashish Verma of Civil Engineering Department, IISc carried out an extensive study to analyse how drivers' vision  influences road safety.

Statistics indicate that 250-300 people die daily in road crashes in India. “That is like a jet plane crashing daily, and no one says a word about it”, says Prof. Ashish Verma. Driver error is the cause in about 78% of road accidents. In one of his recent projects, Verma and his team studied how visual abilities of the driver affected road accidents.

The study revealed that, among those who volunteered for the study, more than half (52%) had at least one vision disability. The team used data analysis methods to evaluate influence of visual disabilities on the crash involvement. They observed that the crash involvement of drivers with at least one visual disability was 81% higher than drivers with no visual disability at all.

The team carried out tests on 387 professional drivers from from Karnataka Road Transport Corporation (KSRTC), Bangalore Metropolitan Transport Corporation (BMTC), and Vijayanand Road Lines (VRL) who volunteered for the study. Some volunteers came from IISc itself and a few others were learning licence and license renewal applicants from Road Transport Office (RTO). Team obtained crash history for the volunteer drivers from organisation data. Where such data was not available, as in the case of IISc volunteers for example, the team used a structured questionnaire to get crash history.

Any person can give a self declaration about his or her medical fitness to qualify for a license test in India. Vision acuity is tested only for commercial vehicles. Prof. Verma and his team identified six more properties that influenced visual abilities. These are colour vision, binocular vision or phoria, depth perception, contrast sensitivity, glare recovery, horizontal field vision and vertical field vision.  Depth perception is very important when overtaking vehicles on a road with a divider. If the driver cannot judge the speed and distance of the vehicle coming from the opposite side, the risk of a crash increases. Contrast sensitivity is being able to identify an object from its background. Horizontal and vertical peripheral vision deals with the ability to sense movement on the sides, above, and below while looking forward. “Glare is the sensation caused when bright light is flashed in front of the eyes and vision is obstructed for a couple of seconds. Recovery from glare is important during night driving as oncoming vehicles use high beam. Glare increases reaction time in drivers, compromising safety” explained Prof. Verma.


Prof. Verma and his team used a vision screener instrument  to test various visual functions mentioned earlier. The volunteers were then classified as ones having acceptable vision and unacceptable vision.

 Though people with no visual disabilities were also involved in road crashes, the results of this study show a significant relation between road crash tendencies of drivers and visual defects like phoria, peripheral vision and contrast sensitivity.

There are multiple other factors affecting road crashes. Accidents may be caused due to bad road conditions, environmental factors or psychological condition of drivers. However this study underlines the importance of visual requirements for safe driving.

Prof. Verma suggests that vision parameters like peripheral vision, contrast sensitivity and glare recovery in addition to general acuity must be tested for commercial and public service vehicle drivers to begin with. The governing laws regarding driving license procedures need to be appropriately amended. “Strict visual screening before issuing a driving licence can help create safe drivers and crash-free roads” he signs off.


Prof. Ashish Verma is Assistant Professor in Department of Civil Engineering, Indian Institute of Science, Bangalore

The paper “Assessment of driver vision functions in relation to their crash involvement in India” was published in the journal Current Science, 25th March 2016 issue.