Portsdown Hill Road & James Callaghan drive are a set of roads along the top of Portsdown Hill that is currently used by a lot of cyclists for commuting, touring and leisure facilties due to the forts, views and open areas around it.
As such, it's a well known tourist spot to stop for a burger or take a picnic and fly a kite.
However, being on top of an exposed hill results in significant side winds which results in cyclists being blown about by gusts, and therefore all cyclists need to take primary position on this road to give them space. As a 40mph road, many drivers have significant issues with cyclists taking primary, and therefore perform many punishment/close passes.
The affect of this on cycling in the area is many
1) More people would cycle from the surrounding areas ( Waterlooville, Havant, Fareham/Lee on Solent ) to work at QA Hospital or the businesses on the hill if there were better cycle infrastructure.
2) More people would cycle from the surrounding area & to enjoy the space & views if it felt safer to get there.