The A3100 is the original alignment of the A3, before the Guildford and Godalming bypass was built in the 1930s. As you might expect, it runs right through the centre of these two towns.
London Road, Guildford
The road begins at Burpham Interchange with the A3. This junction (which only has east-facing slip roads) is in two different parts, each meeting the A3100. Both join at a roundabout several hundred yards later. The road then goes through Burpham, meeting the B2234.
The road then enters Guildford. All through traffic leaves via the A25 and A246 but the A3100 continues into the town centre and runs down the northern section of the High Street before a set of traffic lights is reached and this section of the A3100 ends with all traffic forced right onto the A320 (which also ends here).
The road restarts at the Friary Bridge gyratory, along with the A281, A31 and A322. It then runs along Park Street to reach the western end of the High Street to rejoin the old A3. It follows this out of town, terminating the A248 and B3000 before reaching Godalming. Here the road bypasses the semi-pedestrianised town centre, with the B2130 terminating on the bypass. It then returns to the old A3 route to Milford, terminating the A286 at a mini-roundabout before ending itself a short distance further on at traffic lights on the A283. Turn right to return to the A3, although southbound traffic can cut off the corner by turning left instead.