More money from the Dartford Crossing tolls should go into making the tunnel safer for motorists, the AA has said.
Drivers' stress levels rise when approaching the tolls, a survey says
The AA has called for the government to invest in a series of measures to protect drivers using the tunnel, following a Europe-wide survey.
The study, which assessed 28 tunnels in 10 countries, was commissioned by ADAC the German equivalent of the AA.
Dartford was one of six tunnels rated acceptable - 18 were very good or good with one poor and three very poor.
Inspectors praised the day-to day running and management of the Dartford Tunnel as well as the fire detection and ventilation equipment.
But they highlighted the need for more video surveillance cameras, better maintenance of carriageway edge markings and soundproofing of emergency phones.
The report found emergency lighting, better escape route signing and heatproof cables were also needed to raise the tunnel's rating to good.
Bert Morris, said: "Since the Dartford Crossing reverted to public ownership last year, a surplus toll revenue of some £60m is sitting unused and unallocated in the bank with more motorists' money accumulating everyday.
"This money should be used in the first instance to bring Dartford up to the standards that are now the norm across much of Europe.
The funds should also be used to improve safety in London's other road tunnels and to build new Thames crossing."
The government has said all the money from the Dartford Crossing toll would be ploughed back into transport improvements.