This road leaves the A1Barnet bypass at a simple GSJ. The four slip roads all meet at an 8-shaped roundabout before a short dualled section leads to a gyratory. The A5135 bears left here onto Elstree Way, where a 30mph speed restriction applies. We're no longer dual, although there's a service road to the left suggesting that maybe we were planned to be.
After twin roundabouts leading to the industrial estate we become definitely S2 and we bear round to the left to end at a final roundabout on the B5378.
What is now the A5135 was originally unclassified but gained its number in the 1960s. At the same time, part of the B5378 as far as the A5 (now A5183) at Elstree also became the A5135, but this was quickly downgraded back to the B5378.