This week's Good Cycling Facility is probably the closest we've seen to a genuine cycle street in the UK, located on the Taff Embankment in Cardiff, Wales.
Principally a Sustainable Urban Drainage Scheme (SUDS), the scheme has involved the planting of new trees and rain gardens, as well as the removal of all on-street parking on one side of the road. A smooth asphalt surface for cycling has been added, with a rough median to discourage overtaking, and a 20mph speed limit. These measures help to establish cycling as the principle mode of transport on the street.
It's not perfect - there is a little too much through traffic for the street to feel comfortable to cycle on at all times, and measures should be taken to remove it. But it's a bold scheme that could serve as the template for future projects across the UK!
(You can read more about this scheme on The Rantyhighwayman blog)