In a highly critical report, the NAO claims that the agency lags behind some overseas counterparts in adopting technology to deal with traffic problems. It says that the agency has managed some of its trials poorly and that, even when trials have been successful, it has failed to roll out fresh ideas across the network.
The NAO points out that the agency has installed sophisticated third-generation message signs on motorways in the North and Midlands but has not done so on equally congested motorways in the South East. It installed first-generation signs on motorways in the South East in 2001 but then changed its mind as the older signs were not appropriate for traffic volumes.
The mistake cost the agency £70,000, according to the NAO.
Its report adds that the agency should be consulted in the licensing of major events so that it knows about them in time to make provision for extra traffic.
The agency insisted that since the audit it has embarked on initiatives such as car-share lanes and reviewing how it assesses pilot projects.
An updated traffic control centre will be fully operational next year, it added.
Tackling Congestion by Making Better Use of England's Motorways and Trunk Roads can be viewed via www.PlanningResource.co.uk.