BUSES will take over from trains when Strood Tunnel is closed on January 17 so that it can be repaired for 70mph train operations.

The mile-long tunnel between Strood and Higham will stay closed for a year. When it reopens, the 20mph speed limits that have dogged rail journeys along the Kent Coast Line since December 1999 will be lifted.

The restraints were imposed after a series of rockfalls thought to have been caused by the creation of the Wainscott by-pass.

Most of the tunnel remains as it was originally dug out in the 1810s. At that time it was used to carry canal boats with provisions and weapons for the dockyard and its defences. But 30 years later it was turned into a rail tunnel.

Network Rail will be reinforcing the sections of tunnel that are currently unlined. That means using steel support arches and concrete lining. A new drainage system will protect the line from rising water levels from the Thames and Medway Rivers. The tracks will also be renewed.

It is the longest tunnel reconstruction project for many years on Britain's railways. It is also the country's oldest rail tunnel. Strood and Higham stations will stay open for the replacement bus service.

Train services between London and Higham will run to the published timetable. Off-peak Charing Cross to Gillingham services will terminate at Higham. A half hourly service will run between Strood and Gillingham.

• The tunnel was forced to close on December 23 after yet another chalk fall. Rush hour travellers were left stranded at Higham and Strood stations for more than two hours just after 7am while the fall was investigated.