Bearing in mind this is your first post, I hope you'll understand the skepticism.
Who are you? A marketing/PR type floating ideas for a client?
Where do 13 miles and 1,000 riders come from?
You've contacted the Police to confirm they'll close the roads, or is it just that someone has had them closed before?
If it's a race, then what are the qualifying criteria? Just a chunky entry fee or will there be heats.
1,000 people and timing chips sounds more like the sort of thing laid on to massage the egos of Full Kit Wankers, than an actual race.
Are you in contact with #EC1Collective ?