Work to improve traffic flow at a busy junction of the M40 in Oxfordshire is set to begin.
The five-month scheme, starting on Monday, aims to reduce congestion at junction 9 near Bicester where the motorway meets the A34.
The Highways Agency project will increase capacity by adding a lane to the busiest parts of the junction.
Motorists have been warned to expect some delays, although no lanes will be closed during peak times.
Surinder Bhangu, project manager, said: "Peak-time congestion is a real problem for drivers on this busy section of road.
"We have planned every section of this project carefully to keep delays to road users to an absolute minimum.
"Throughout the work, there will be no reduction in the number of lanes available to road users during peak periods, and when we do need to temporarily close lanes or slip roads we will do it overnight when traffic flows are lowest."