The Highways Agency (HA) took five years to complete the procurement of a digital information system for England's motorway network - twice as long as planned.

But according to a National Audit Office (NAO) report into the project, the organisation successfully transferred the risks involved to the private sector bidder.

The procurement followed a 17-month shortlisting process which started with six potential bidders and left just two in the running for the contract, which concluded in 2005. But the agency spent £15.5m on professional advice - more than £10m above its initial budget.

"The Highways Agency's procurement identified the risks to the National Roads Telecommunications Services project and successfully transferred them to the private sector, conducting negotiations with the preferred bidder well,” said NAO head Tim Burr.

“However, it did take a lot longer than planned and only two bidders remained through to the end of the competition. There are good practice lessons both for the agency and for other major public procurements."

HA hoped to reduce congestion on the road network with the system, which provides moment-by-moment information on traffic congestion and delays.

In 2005, the HA contracted supplier GeneSYS Telecommunications to replace England’s ageing motorway network system - in place for the last 40 years - for a digital platform to carry data as well as CCTV images.

The supplier was given a two-year deadline to replace the obsolete system and the project and 14,000 road side devices were delivered on time, according to the HA, which pays the supplier £3.9m per month.