Roland Perry wrote:
at 18:31:57 on Fri, 20 Jan 2012, John Levine remarked:

I'm not sure why any agency would go the smart card route for tolls.

Instead of cash, for non-regular users. There's a toll bridge/tunnel at
the Thames Estuary, for example, and while they have a transponder
scheme my usage of the crossing when I lived nearby was only perhaps
once a year. A contactless credit card seems a better bet than adding
interoperability to any particular transport smart card though.

We already have interoperable toll transponders with E-ZPass.

Off-hand I can only think of three toll routes in the UK, plus the
London Congestion Zone (which I think doesn't have a transponder).

I realise toll routes are much more common in the USA.

I didn't realize there were no transponders. It's enforced entirely
with photographs of license plates?