Here's an interesting piece on intelligent transport from Roland Piquepaille's Technology Trends -
This is an extract from the post 'Networks on Wheels':
"More and more cars and trucks are equipped with some kinds of wireless networking devices, helping to create applications based on vehicle to vehicle communications. But these types of networks present some new security challenges because of the short contact times between different mobile nodes and of the large size of these networks. This is why Germany's funded Network on Wheels (NoW) project has decided to apply security considerations right at the beginning of the network development. Read more...
Let's start with an example picked from "Trusted Network on Wheels," an article published by ERCIM News No. 63 in October 2005. "As soon as two or more vehicles are in radio communication range, they connect automatically and establish an ad hoc network, and create a new security threat" (Credit: BMW Group Research and Technology).
The NoW project has produced many documents, but if you're interested in this last part, here is a paper I recommend: Attacks on Inter Vehicle Communication Systems - an Analysis (PDF format, 11 pages, 741 KB).