University researchers in the Netherlands and Germany have demonstrated
that cars equipped with technology that allow them to communicate with
each other and highway infrastructure, presumably to avoid collisions
and jams, could be snooped on to track vehicles' locations. The US's
National Highway Traffic and Safety Administration (NHTSA) is
considering mandating the connected vehicle wireless communication
protocol as son as 2017.
http://www.wired.com/2015/10/cars-that-talk-to-each-other-are-much-easier-to-spy-on/