THE effects of ageing on driving related performance

According to one estimate, about 40 percent of the driving population will be over the age of 60<br/>by the year 2020 in the UK and currently, several hundred thousand drivers with dementia hold<br/>driving licenses. The number of motor vehicle crashes per unit distance of automobile travel is<br/>“U”-shaped, with risk increasing slightly between the ages of 55 and 60, but risk increasing with<br/>each successive five-year interval. Some individuals who have mild dementia possess sufficient<br/>driving skills to be designated as fit drivers. The most challenging assessment and decision for the<br/>physician/licensing authority as regards fitness to drive lies in drivers who are questionably<br/>demented or are in a state of very mild dementia.<br/><br/>In the absence of a reliable standard protocol, some clinicians make judgment based on selfreporting,<br/>which has risks associated with it as lack of insight and judgment are potential common<br/>traits of the population experiencing cognitive decline. Seldom is recourse made by health<br/>professionals to on-road assessment as a first alternative as it requires a fee and such testing<br/>centers are not readily available everywhere. This research addresses this issue of the<br/>identification of cognitive tests that can be used to assess an individual’s ability to drive and<br/>especially of those individuals that are questionably demented and are the most difficult to<br/>identify. A younger and an older group consisting of 56 drivers in total were administered nine<br/>different cognitive tests and two drives (Drive-I and Drive-II) on the STISIM driving simulator.<br/>The cognitive test ufov3 (involving the identification of a central target and simultaneously the<br/>radial localization of a peripheral target embedded in distracter triangles), which is the third<br/>subtest of the UFOV (Useful Field of View) test showed the highest discriminating ability in<br/>separating “poor-drivers” from “not-poor-drivers”, with 92.86 % of the drivers correctly<br/>classified. The next best discriminating ability in decreasing order of strength was that of dichotic<br/>listening test, trail making test, rey-copy test and paper folding test. Also, age was found to be an<br/>excellent discriminator of “poor-drivers” and “not-poor-drivers” with 91.07 % of the drivers<br/>correctly classified. A composite cognitive measure consisting of the sum of all nine cognitive<br/>tests was not a better predictor than the ufov3 test alone; overall it was still an excellent<br/>discriminator, classifying 89.29 % of drivers correctly. The commonly recommended Clock<br/>Drawing test and the Trail Making test did not emerge as significant predictors of driving ability.<br/>A general driving skills linear model for prediction purposes was derived that explained 59 % of<br/>the variation in a general driving performance index with the ufov3 test, the dichotic listening test<br/>and the rey-recall test as significant predictors. Recommendations are made as to how this test<br/>should be used to screen potentially at risk drivers.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2009

Author dc:creator

• Khan, Muhammad Tariq

Advisor dc:contributor.advisor

• McDonald, Mike