The sigma 30 f/1.4 will probably do you fine, but why not go for a 50 f/1.4? If you shoot Nikon or Canon that's a great lens, and it gives you extra mm range.
The Nikon/Canon 50 f/1.4 is cheaper than the sigma too.
As for distance, that shouldnt be a problem unless you are like RIGHT THERE! next to the bikers. Seriously, unless the "path" is the size of a small child, you'll be fine for distance.
EDIT: Wait read this wrong. WHY are you that close to bikers (I'm assuming these are bikers as they are speeding by?).