BT introduced the Virtual Fleet Risk Management (VFRM.net) system in a bid to reduce accident rates.
About 20,000 of BT's 70,000 employees are completing the training, which identifies high-risk drivers so they can be helped to reduce the likelihood of crashing while on the road.
Dave Wallington, group safety adviser at BT, said: 'A conventional approach to defensive driver training is unrealistic for the number of drivers we employ. We needed something that could filter those drivers assessed as being at high risk.
'We can then look at the identified areas of weakness and tailor courses. VFRM.net offered us a cost-effective solution to driver assessment, rather than the usual generic approach of on-road training.
'Initial results suggest there is a strong correlation between driver scores and accident rates, so we are correct in using VFRM.net as a tool in accident reduction.'
Napier University in Edinburgh is using the results of BT's online assessment as part of a study into at-risk fleet drivers. It has found that there is a clear link between high-risk drivers and accident involvement.
The study found that 5% of a sample of drivers who had taken the test was responsible for 45% of the crashes.
It also found that drivers with the worst scores in the online assessment were at least three times more at risk than those with the best scores.