The B3040 was an urban B-road through the northern suburbs of Southampton. It is not known when the road came into being, although it had gained its number by the mid-1950s. It is now the A3035.
Starting on the A33 in Southampton Common just south of Bassett Crossroads, the B3040 passed through Highfield to A335 at The Mitre, Portswood. After a staggered crossroads, it headed down the hill, through St Denys, to Cobden Bridge. After Bitterne Triangle it turned right, ending on the A3024 at Bitterne Station.