Beginning on the A1 at a signalised crossroads, the A512 heads north along the dual-carriageway Blacks Road to Blacks Road Interchange, M1 J3, where the road TOTSOs left. Continuing as a D2, it soon TOTSOs again at a roundabout and becomes S4 with a central hatched area. After a roundabout with the B102, the road narrows, losing its hatched area, and takes on the original southern end of that road. At a signalised T-junction (formerly a roundabout), the A512 TOTSOs a third time, with the A513 continuing straight on. Heading south now, the road is S2. It quickly ends back on the A1 at Queensway Roundabout.