The B388 connects the towns of Egham and Chertsey in northwest Surrey, running for the most part a little to the east of the M25.
The route starts at a junction with the A30 and A308 at the Runnymede Roundabout on the northeast side of Egham. The first 450-m stretch heads into Egham along The Avenue and part of the High Street (the pre-bypass route of the A30) before the B388 turns left at a mini-roundabout junction with the B3407 just before the town's fire station and heads east along Vicarage Road.
We go under the M25 and then, swinging round to the right, over the London Waterloo to Reading railway line by means of a level crossing. Some 900m further south we dogleg left-and-then-right through a pair of mini-roundabouts: the straight-ahead route at the second of these is the B3376 leading into Thorpe Lea.
Shortly afterwards, Clockhouse Lane East comes in on the right: this was the original route of the B388, which left Egham via Station Road and Stroude Road, but was severed by the building of the M25; hence today's route out of Egham.
At Crabtree Corner the B388 swings to the right to run alongside the M25 and bypass Thorpe (originally it went through the middle of the village). After skirting the northeast side of Thorpe Interchange and crossing over the M3 the B388 resumes its original course as far as a roundabout junction with the A320 near the Twynersh public house on the edge of Chertsey. Here our journey ends, the A320 today having taken taken over the final 900 m of the B388's original run into the town centre.