Early models of driverless cars are actually expected to operate more cautiously than regular vehicles, resulting in a possible decrease in "effective capacity and a decline in network performance", the report warned.

Researchers found that the performance of driverless cars is dependent on the behaviour of the vehicles around it, so the benefits of the technology may not be felt until they make up the majority of vehicles on the road.

Moreover congestion levels will not drop significantly until automated vehicles make up between 50 to 75 per cent of the fleet and are able to perform at their full capacity, the analysis suggested.

Steve Gooding, director of motoring research charity the RAC Foundation, said: "There's a prize to be had in terms of swifter, safer journeys, but the transition to that world will be challenging.

"There are around 32 million conventional cars on the UK's roads - as driverless cars come in, traffic flow could initially get worse rather than better, potentially for many years.