Drivers will be diverted off the A421 for four nights as the highway is closed both ways for maintenance.
Diversions will be in place from Wednesday, February 3, between the junction with A4280 St Neots Road and the A6 to allow Highways England to carry out renovations to the eastbound and westbound bridge.
Project Manager at Highways England Anna Graham said: “We’ll be carrying out the repairs to the bridge overnight when it’s generally less busy – minimising disruption to drivers. This work is necessary to ensure smoother and safer journeys.
“I’d urge motorists to plan ahead and allow extra time for their journeys while the work takes place.”
She added there will be a clearly-signed diversion route via the A6 Ampthill Road, Rope Walk, Longholme Way, Newnham Avenue and A4280 Goldington Road to re-join the A421 at Renhold interchange.
Work to the bridge will be carried out from 8pm and 6am and is due to finish on Tuesday, February 9, dependent on weather conditions.