|Location Map ( geo)|
|Distance:||8.2 miles (13.2 km)|
|Meets:||M1, A43, A5076, A4500, A508, A428, A4500, A5095, A5101, A43, A5076|
|Route outline (key)|
The road starts at M1 J15A as the northern extension of the A43. The road is initially primary dual-carriageway as it heads due north to a roundabout on the A5076 (original A45 Northampton bypass). There's a multiplex east along that road to another roundabout where the pre-M1 line of the A43 is reached, where the A5123 regains its number and heads north into the town centre.
We reach the inner ring road at a roundabout on the A4500 to the west and A508 to the north, whilst we turn right and become the dominant number in a multiplex with both. One block east we reach a gyratory where we go round three sides of a square (westbound traffic simply follows the fourth side). The A508 turns off here heading south; this is where we lose primary status. The A5123 then continues anticlockwise along the inner ring road across a roundabout and a few sets of traffic lights and soon reaches a final set of lights back on the A508, which took the western side of the ring road. The mainline of the A5123 has already turned off, however, by making an illegal right turn onto Abington Street (heading clockwise along the ring road the left turn is obligatory).
We meet a gyratory just afterwards where the A4500 regains its number by bearing right whilst we bear left. We now head northeast along the residential Kettering Road to pass a park and cross the A5095 at traffic lights at the far end. The road remains residential through the suburb of Kingsley Park to reach the A5101. This was originally a sharply angled fork but is now a roundabout, although the location of the fork is still obvious. The road becomes more suburban as it continues to the northeast. Presently it crosses a roundabout and then turns sharply right, deviating from the old A43 to a further roundabout where it ends on the present A43 and A5076.
If you weren't confused enough by the current route of the A5123, then it's history will really twist your brain. From the little mapping evidence so far discovered, the earliest mention of the A5123 number is on the recently completed St Peters Way on the south side of the town centre, which is now the A428 for the western half, but remains part of the A5123 route, in a multiplex for the eastern half. Later maps show that St Andrews Road north past the station was also part of the A5123, but changed end-on to the A508 at the A428 Grafton Street crossroads. The same map shows the eastern side of the inner relief road is also the A5123, suggesting that with a multiplex along Grafton Street the A5123 did a full circle of the town centre.