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What is a safe following distance?

Confusion over what is a “safe following distance” has QUT road safety researchers calling for a standardised definition to prevent tailgating.

First published 11 October 2017
  • Tailgating conclusively linked to rear-end crashes
  • Most drivers leave less than a 2 second gap between them and the vehicle in front
  • Rear-enders account for one in five Queensland crashes

Dr Sebastien Demmel, from QUT’s Centre for Accident Research & Road Safety – Queensland (CARRS-Q), said the results of the study which found 50 per cent of drivers tailgate, was being presented at the 2017 Australasian Road Safety Conference in Perth today.

“This study, for the first time conclusively linked tailgating with rear-end crashes, but we also identified confusion among drivers over what is deemed to be a safe following distance,” he said.

“Despite drivers perceiving they are following at a safe distance, our on-road data showed that in reality most don’t leave the recommended two to three second gap,” he said.

“At some locations 55 per cent of drivers were found to leave less than a two second gap between them and the vehicle in front, and 44 per cent less than a one second.”

The study used Queensland state road crash data to pinpoint rear-end crash blackspots, and on-road monitoring to determine driving conditions, speed and tailgating. More than 500 drivers were also surveyed on their perceptions of driving behaviour and their knowledge of safe following distances.

Dr Demmel said it was concerning that most drivers reported keeping the same gap regardless of traffic flow or road type.

“One of the reasons drivers may not be leaving a safe following distance is because 60 per cent used metres or another unit of distance rather than the recommended seconds to assess a safe following distance.

“When using metres compared to seconds, the gap between vehicles changes, however most drivers said they kept the same gap length regardless of traffic flow or travelling speed.”

Dr Demmel said rear-end collisions account for around one in five crashes on Queensland roads and contribute to 25 per cent of the total cost of claims to the Queensland compulsory third party (CTP) scheme. 

“If we can reduce rear-end crashes, we will see a reduction in crashes and the number of people being injured, which will lead to a corresponding reduction in CTP premiums,” he said.

This project was funded by the Motor Accident Insurance Commission (MAIC), the regulator of the Queensland CTP scheme. CARRS- Q acknowledges in-kind support from MAIC and staff from the Queensland Department of Transport and Main Roads and Queensland Police Service.

The 2017 Australasian Road Safety Conference draws together experts from across the globe to share the latest in research, programs and developments with the aim of reducing injuries and deaths on our roads.

Media contacts:
Sandra Hutchinson, QUT Media, 07 3138 9449 (Tue/Wed) or
After hours: Rose Trapnell, 0407 585 901


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