For urban roads managed by local authorities congestion is measured as person journey time per mile on a set of key routes into urban centres in the 10 largest urban areas in England. The first performance information showing change against the 2004-05 baseline will be included in the Department for Transport autumn performance report to be published at the end of 2007.
For strategic roads managed by the Highways Agency congestion is measured in terms of delay on the worst 10 per cent of journeys. The first performance information, relating to a subset of the network, was published in the last autumn performance report, in December 2006. The next performance information will be published in the department's annual report in about a month's time.
Data for earlier years are not available on the same basis.