The online fleet risk assessment completed by Data Programmes, part of the Fleetsafe group, used a series of multiple-choice questions to assess individual risk on the road.
A fifth of drivers were classed as medium risk with 5% in the high risk bracket.
All should be provided with training, according to Steve Harris, Data Programmes' chief executive.
He said: 'We would recommend driver training for employees who receive a medium to high risk rating or higher. The training may be specific to one aspect of their driving, for example reversing or how to assess appropriate speed or hazard perception.'
Almost half of the drivers polled (45%) were classed as low to medium risk, with 30% being rated medium risk. However, training will still be offered despite them being in a lower risk category.
Harris said: 'Employees who are given a medium rating will be offered additional e-training or classroom-based seminars to reduce their risk rating, while drivers with a low to medium-risk rating will receive on-going awareness information from ourselves.'
The number of fleets offering training to drivers is way behind what it should be, according to Harris. He believes this could be putting other drivers in danger.
He said: 'The vast majority of employees assessed come from health and safety-conscious fleets. Evidence suggests that most of Britain's fleets have so far failed to focus on risk management and therefore the risk rating of many employees yet to be assessed will be high.
'Not only are these drivers putting themselves and other road users in danger, but companies are increasingly putting themselves at risk of criminal or civil prosecutions in the event of a road accident involving an at-work driver.'