Only half of UK motorways have received the top four-star ranking, following a survey by the European Road Assessment Programme.
The star system has been introduced by EuroRAP - a sister organisation to EuroNCAP - to grade major roads worldwide.
The UK's dual carriageways fared even worse. Only 22 per cent received four stars, while two-thirds of single-carriageway trunk roads received a two-star rating.
Dr Joanne Hill, director of the Road Safety Foundation which carried out the research, said, "Our assessment of trunk roads considers three key elements: the protection provided if vehicles run off the road, the risk of head-on collisions, and the safety of junctions.”
The road rated least safe was a 9.5-mile stretch of the A5 between Daventry and Rugby.