Millions of motorists a day suffer traffic jams on England's roads because the Highways Agency has been slow in tackling the problem, a report says.
Traffic congestion costs industry £3bn a year, the report said
The National Audit Office (NAO) said the agency was too concerned with risks to try new ideas, had run trials poorly and could spend its money more wisely.
Road congestion was costing industry and commerce £3bn a year, the NAO said.
Highways Agency chief executive Archie Robertson said steps were being taken, but accepted there was more work to do.
Between 1995 and 2002, the amount of traffic had risen by 14% on all roads and by 26% on motorways.
The report said traffic speed had improved between 1998 and 2003 but was still slower than the 1995 level.
The NAO said the agency was "too risk averse" and behind its European neighbours in introducing innovative measures to tackle congestion.
These include lanes dedicated to specific vehicles, lanes that can change direction, opening the hard shoulder during busy periods and variable speed limits.
The use of such measures in England - the bus lane on the M4 in London and variable speeds on the M25 - remained limited, the report said.
Keith Holden, the NAO's director responsible for transport, said: "There are 31m vehicles on the roads on this rather small island.
"Congestion is a current problem and the government needs some quick wins.
"Building roads or widening them takes many years and it needs to look at programmes that make quicker wins."
The Highways Agency spends £200m a year on its Making Better Use programme, aimed at bringing quick relief from congestion.
The NAO said it did not believe money had been wasted, but that the agency needed "a smarter approach in getting the best out of the capacity".
"It needs to adapt the programme better than it currently is."
The report recommended giving motorists more information en route, better targeting of technology on the busiest roads, better preparation for major events that can cause jams and improvement at dealing with incidents and accidents.
STEPS PLANNED BY THE HIGHWAYS AGENCY
Car-sharing motorway lanes
Use of hard-shoulder on M42
Deploy 1,200 traffic officers
Edward Leigh, chairman of the Commons public accounts committee, Edward Leigh, said the agency was "timid and irresolute in taking advantage of congestion-reducing measures that don't involve road building".
"The Highways Agency's own thinking needs to start flowing freely," he said.
"It must adopt a more pragmatic and visionary approach to new technologies, so that the
best of them can start to be used to tackle traffic jam misery."
The report said that a quarter of all traffic jams were caused by accidents and roadworks, but sheer weight of traffic led to two-thirds of congestion.
NAO head Sir John Bourn urged the agency to carry out more effective trials of proposed congestion-reducing measures, and implement them more widely if they were successful.
SUGGESTIONS FROM THE NAO
Give motorists more en-route information
Target most appropriate technologies on busiest roads
Be better prepared for major events and accidents
Mr Robertson said the agency accepted it needed to implement projects more quickly and said it would review how it assessed pilot projects.
He said: "I will ensure that where recommendations for improvements are safe and appropriate to deliver, we take action."