Hi Bakerboy, I did this race last year. It's probably not a great PB race, as it is verging on hilly. Actually, there's not a huge amount of flat, so unless your previous best was on a undulating course, or your form's much improved, it'd be tough to PB. As to the traffic free thing, I can't honestly remember, but there were parts through a park (on paths) and I certainly don't remember much traffic.
Hope that helps,
Mowgli