The B430, having just left the A34, is on the original A43 alignment here, meeting its newer counterpart for westbound A34 traffic
The B430 is the former A43 between what's now the A34 and the M40, where the A43 route now begins. It's a useful shortcut between the two.
It starts at a grade-separated junction with the A34, with eastbound traffic taking a straight fork using the original line of the A43 whilst a new link road was built for westbound traffic. The road then heads north through Weston and past the associated RAF airfield. As befits a former primary route, the road is fast up to Middleton Stoney, where there's a set of lights with the B4030 in the middle of the village. Indeed, the A4095 gives way to us at a staggered crossroads a mile further south.
After that, it's back out into the countryside briefly before we pass through Ardley and meet the M40 at junction 10. The road turns into the A43 begins at the first of that junction's three roundabouts.
The route of the B430 was originally numbered A43, which started near Oxford. When the A34 was improved to meet the M40 at junction 9, it took over the A43 as far as what's now the eastbound A34-B430 offslip - the road ahead being the A421. The junction was a simple fork in the road, with the grade-separated sliproad for westbound traffic added later.