The narrow, undulating road between Milngavie and Croftamie was the scene of 24 fatal or serious crashes between 2006 and 2010, according to the Road Safety Foundation (RSF).
It is now the third most dangerous road in the UK following a 41% rise in accidents and the high volume of traffic using the route, the pressure group said.
Fiona Risk, convener of Milngavie Community Council, claimed she was surprised the road was classed as such a high risk. She said: "It's quite a twisty road and I think it's got a lot to do with the speed of the traffic on the road, but I didn't think it was the most dangerous in Scotland – that's quite a shock.
"I would have thought it would have been the A9."
She added: "There are already warnings on the road, so I'm not sure if any other measures would make a difference – they only work if people obey them."
The European Road Assesment Programme, which tracks accident rates and road conditions, gave the stretch of A809 a rating of 195, coming behind only the A537 between Macclesfield in Cheshire and Buxton in Derbyshire, which has a rating of 516.8, and the A5012, also in Derbyshire, which sits at 239.5.
The review also reveals the risk of death or serious injury on Scotland's motorways and A roads is higher than anywhere else in Britain. However, fatal and serious crashes north of the Border account for just 12% of all similar incidents in the UK.
The UK Government is to review the finance and ownership of major road networks and the RSF is calling for safety to be made central to any reform. It claims busy, higher-risk roads should be seen as a priority.
Joanne Marden, director of the RSF, said: "The planned reform in road financing means a new focus on measuring safety performance and the high returns quickly available from safety engineering. Where there is clear evidence of higher-risk and heavy traffic flows, the economic case for intervention is compelling.
"With 2% of GDP [gross domestic product] lost in road crashes as well as lives, we can get quick, guaranteed returns by raising safety levels."
Meanwhile, it has been revealed Scots involved in accidents are less likely to make a claim for whiplash or injury than their UK counterparts.
A study by the Institute and Faculty of Actuaries shows Scotland has the lowest ratio of third-party injury claims to third-party damage claims of anywhere in the UK.
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