I called earlier for ideas for uses of ad-hoc wireless card data networks (with 802.11 or similar.) I've been having trouble finding any compelling because I think the space is narrow, especially for the driver. I don't see much data you will want that only other cars around you will have. It has to be fresh, live data (otherwise your car would have loaded it when parked) and it has to be giant data (otherwise you would pick it up over the 3G or 4G cellular networks at lower data rates) and not suffer from both the connectivity and the data availability being intermittent and random in nature.

However, seeing the Dresner paper on a Reservation-Based Intersection Control Mechanism (with cool simulations) made me wonder if we might be able to get something sooner.

People might be too scared of the technology to handle a high-volume intersection but what about a low volume one, such as a 4-way stop? In particular, what if we have to assume many cars don't have a network?

A networked 4-way stop would have a network node broadcasting its existence and state. If the node at the intersection were down, it would act like an ordinary 4-way stop. Networked cars approaching the intersection would broker travel through it. (They would all have GPS, 802.11 and the node at the intersection would have a map.)

If a car was given access, right lights on the stop signs would light up. (Their power needs are much less than a traffic light, possibly even solar.) The one with the cleared car would light yellow. The cleared driver would get a signal (audio and visible) that they are cleared, inside their car.

Drivers seeing the red light would stop (network enabled or not) and wait for the light to go off after the cleared cars go through. Drivers seeing the yellow light who are not the cleared car (and thus not a networked car) would stop and proceed through the intersection like a normal 4-way stop.

The cleared driver would approach the intersection at reduced speed and check for drivers stopped at the other signs. If there were none she would move through the intersection without stopping. If some were present the display would say which intersections had networked cars. If all were networked, the driver woudl proceed. If some are not networked, the driver would proceed with more caution (perhaps a 5mph rolling stop, ready to full-stop if needed) or speak a command or push a button to enhance the stop signal for the non-networked cars....Of course, if you are willing to spend a bit more money on the intersection, but not quite ready to make it a full fledged "traffic light" intersection, there are more things you can do.

Since we are planning this for low-use intersections, the lights would get low use. They would not be on unless a networked car was coming through. This inherently makes a cheaper set of lights. Today, traffic lights are all-LED anyway, and much lower power. One that only puts the red light on when the networked car goes through (but which presents a much cleaerer "you have to stop" red light) could be a lot cheaper than the $170,000 that full intersections cost.

Of course, if you can put in car sensors you can do even more with the non-networked cars, but do you want to trust your life to the accuracy of those sensors? Probably not.

Of course, some of these ideas scale up into full traffic lights which can, at a minimum, be smarter about knowing when networked cars are coming. I would get a network node even if it meant that the left turn arrow 1/4 mile ahead turned green for me just before I got there because it heard from me far enough in advance.

The networked cars that do not have priority at the light would be given advice to slow down so that they would not need to stop at the 4 way stop, that they would be the cleared car by the time they got there.

Eventually everybody would get the network unit, especially as it got cheaper.
Just 802.11 and GPS is pretty cheap today. One could imagine not even needing GPS with other tricks, such as other nodes around the area, or even using other networked cars in the area to do time-of-flight location on one another.

Does this sound scary? This is planned for low volume intersections that today get 4-way stops, 2-way stops or yield signs. The networked cars would still proceed through only at about 10mph until they knew they were clear, so even the worst case accidents would largely damage only cars, not people. Pedestrians might need a button (cheap and wireless) or could just treat it like a crosswalk that's not at a stop-sign.

If this worked, we would actually increase the number of intersections that had stop-signs, at least for the non-networked cars. Of course if the goal of the 4-way stops is to slow traffic like speed bumps, this does the opposite.

There are things to worry about as far as privacy when it comes to 802.11 in cars. It's a good way to track people, and definitely good at measuring their speed, for example.