This is a venture by British Cycling and the broadcaster SKY http://new.britishcycling.org.uk/skyride/news/article/20090528-sky-city-ride-Sky-City-Rides-0
I went on one in Leicester, and have a few observations to make.
As a 'serious' cyclist I found it was too slow, and even with me dawdling, I was travelling too fast for the situation, so I kicked back and chilled.
Then there were the 'free reflective bibs' being handed out, and encouraged to wear by the bloke on the PA. The course was on closed roads, one way, with other cyclists taking part as the only traffic. I rebelled and didn't wear one, as I thought it was a bit too 'nanny state' and 'risk assessed' for my liking.
Then there was the helmet issue. Almost every man, woman, child and dog was wearing one. Personally, I do wear one when screaming downhill on my racer or in heavy urban traffic. I don't when dawdling along a country lane (99% of my journeys by bike), and didn't on the SKYRIDE, much to the consternation of some officials, and the PA man, whose regular, "Get your free reflective vest and wear a helmet" announcements tarnished the spontonaeity of the event for me.
As I had to travel to Leicester to take part, the 140 miles had to be done by car, and the approach to the venue in Leicester, early on a Sunday, was backed up with traffic. I could see people getting frustrated, and then to realise it was because of bikes that they were being held up can't have warmed them to the biking culture, as is the whole ethos behind a SKYRIDE.
I believe the events are just a promotional gimmick for SKY and British Cycling to promote their brand, and nothing to do with getting cycling increased as a mode of transport.
The only way in my opinion to do that is to invest in cycling infrastructure, and make the 3 mile drive into the city an expensive, time consuming and un-economic option.
Sustrans and their national network of cycle routes (a few old railway lines and some stickers on road signs on country roads is not enough. We (the people and the planet) demand good quality cycle paths away from traffic.
As other bloggers have stated, give them the facilities and they will come.
Coning off a city centre once ayear on a summer Sunday is NOT good enough to get people cycling.