I'm extremely familiar with the area, and that particular junction on the A27. Basically it's fast, open dual carriageway, and that junction is the only one for some distance. Apart from the north entrance to the airfield, there is small scenic road opposite (Coombes Road), also it's the only crossing place for cyclists and pedestrians (toucan crossing, I think) and is well-used since it leads to the bridge across the river to Shoreham. The traffic lights have been there for many years.
Incredibly unlucky for this to happen just there; it's pretty much all open countryside to the north (apart from Lancing College, the impressive gothic building seen in the background of some of the videos). All in all, a particularly unfortunate incident; let's hope there are no particularly negative long-term consequences for Shoreham or indeed airshows in general.