There is no link between a tunnel closure and lorries hitting a bridge on a diversion, according to figures collected by Highways England.
Data shows that since the Hindhead Tunnel under the Devil's Punch Bowl in Surrey opened in 2011, a railway bridge in Farnham has been struck by HGVs 39 times.
But when dates of it being hit were compared to the dates the tunnel was closed, it was found that although some matched, the diversion routes had not been activated.
The data was presented to Surrey councillors on Friday.
Matthew Salt, service delivery manager for Highways England, said: “No identifiable strike occurred on the diversion route when the tunnel was closed.”
This came as a surprise to county councillor Wyatt Ramsdale, who said he was “utterly convinced” of a link.
And in a written question, the meeting heard of a “nightmare traffic scenario”.
Councillor Peter Clark, Wrecclesham ward member for Waverley, said signs warning lorry drivers to turn back were “too late”.
He wrote: “This results in complete traffic chaos, danger to pedestrians, broken-up pavements and damage to private property."
Councillors will now meet to discuss the problem again.