Those cats-eyes on the roads can be made much more useful than they currently are. If you mass-produce a PCB with a unique identifier hard wired into each one, with a short-range (~10m should suffice) transmitter and receiver that can act as repeater stations and embed them into cats-eyes, and have
an onboard computer in your car then the possibilities are endless.
Crash reports and traffic jams - notices can travel "upstream" from the incident, being repeated along x number of cats-eyes and warning drivers of the approaching conditions potentially miles in advance. You could have it so one cats eye transmits half a message to cars, the full message to the next cats-eye, which would then transmit the next half of the message to the car to only deliver notices to cars travelling in a certain direction.
Traffic light status - the traffic light would transmit it's colour to the cats eye which would then propogate for a pre-determined distance down the road (set by the range of applicable unique identifiers for each cats-eye), and straight into the cars for audible or otherwise notification to the driver.
Advertising - Companies could pay a license fee to transmit their message to their road's worth of cats eyes so that when you drive down the road your computer can say "next left for half price accomodation at motels'r'us" or whatever. This could potentially fund the project.
Road signs - they can transmit "get in lane" or "stop sign ahead" or the speed limit or whatever to the cats-eyes for notification to your car, which would really help in poor visibility conditions.
Stolen cars - commands could be sent through the network and straight to your cars computer to shut down the engine if your car is stolen.
Tracking - the computer ID can be traced through the network to the nearest cats-eye revealing it's location immediately.
Parking meters - The cats eyes along restricted parking zones can continually transmit parking charge information. If your car receives say 5 of the broadcasts from the same cats-eye it's a safe bet you're parking and the computer can then tell you how much the charges are/ automatically debit the amount from your account by sending your cars computer ID through the network.
Speeding control - by knowing the speed limit on the road from the cats-eyes and the speed at which you are travelling you could get audible warnings about speeding. You can, of course, turn this feature off :)
They would be powered by an in-built solar panel/ battery system or a battery recharged through converting the mechanical energy of the cats-eye being compressed by passing traffic (and thereby compressing a high pressure air sack for driving a tiny generator).