A few weeks ago, in my article on myths I wrote why the development of "vehicle to vehicle" (V2V) communications was mostly orthogonal to that of robocars. That's very far from the view of many authors, and most of those in the ITS community. I remain puzzled by the V2V plan and how it might actually come to fruition. Because there is some actual value in V2V, and we would like to see that value realized in the future, I am afraid that the current strategy will not work out and thus misdirect a lot of resources.

This is particularly apropos because recently, the FCC issued an NPRM saying it wants to open up the DSRC band at 5.9ghz that was meant for V2V for unlicenced wifi-style use. This has been anticipated for some time, but the ITS community is concerned about losing the band it received in the late 90s but has yet to use in anything but experiments. The demand for new unlicenced spectrum is quite appropriately very large -- the opening up of 2.4gz decades ago generated the greatest period of innovation in the history of radio -- and the V2V community has a daunting task resisting it.

In this series I will examine where V2V approaches went wrong and what they might do to still attain their goals.

I want to begin by examining what it takes to make a successful cooperative technology. History has many stories of cooperative technologies (either peer-to-peer or using central relays) that grew, some of which managed to do so in spite of appearing to need a critical mass of users before they were useful.

Consider the rise and fall of fax (or for that matter, the telephone itself.) For a lot of us, we did not get a fax machine until it was clear that lots of people had fax machines, and we were routinely having people ask us to send or receive faxes. But somebody had to buy the first fax machine, in fact others had to buy the first million fax machines before this could start happening.

This was not a problem because while one fax machine is useless, two are quite useful to a company with a branch office. Fax started with pairs of small networks of machines, and one day two companies noticed they both had fax and started communicating inter-company instead of intra-company.

So we see rule one: The technology has to have strong value to the first purchaser. Use by a small number of people (though not necessarily just one) needs to be able to financially justify itself. This can be a high-cost, high-value "early adopter" value but it must be real.

This was true for fax, e-mail, phone and many other systems, but a second principle has applied in many of the historical cases. Most, but not all systems were able to build themselves on top of an underlying layer that already existed for other reasons. Fax came on top of the telephone. E-mail on top of the phone and later the internet. Skype was on top of the internet and PCs. The underlying system allowed it to be possible for two people to adopt a technology which was useful to just those two, and the two people could be anywhere. Any two offices could get a fax or an e-mail system and communicate, only the ordinary phone was needed.

The ordinary phone had it much harder. To join the phone network in the early days you had to go out and string physical wires. But anybody could still do it, and once they did it, they got the full value they were paying for. They didn't pay for phone wires in the hope that others would some day also pay for wires and they could talk to them -- they found enough value calling the people already on that network.

Social networks are also interesting. There is a strong critical mass factor there. But with social networks, they are useful to a small group of friends who join. It is not necessary that other people's social groups join, not at first. And they have the advantage of viral spreading -- the existing infrastructure of e-mail allows one person to invite all their friends to join in.

Enter Car V2V

Car V2V doesn't satisfy these rules. There is no value for the first person to install a V2V radio, and very tiny value for the first thousands of people. An experiment is going on in Ann Arbor with 3,000 vehicles, all belonging to people who work in the same area, and another experiment in Europe will equip several hundred vehicles. With V2V you can't simply get a group of cooperators together and get much value. V2V only works with the cars that happen to be around you at any given instant. Unlike Fax or E-mail, where you could pick a partner anywhere in the world and start using the tool with them, you don't pick the cars that are around you. The Ann Arbor test is trying to get around that by using a group of people who work together. In their case, there is a decent chance, particularly during rush hour, that they will encounter other users, particularly close to the workplace but also on the common commute routes. This will create some V2V encounters that will be learned from.

But in the real world? As I noted, even if 2.5 million US cars had V2V, and you are one of them, only one in 100 of the cars you encounter will be able to talk to you. And the odds that any 2 random cars who might have a collision would have it are 1 in 10,000 -- close to valueless as a collision reducer.

So if a cooperating technology does nothing even for the first million to buy it, it can never take off without a legal mandate. And a legal mandate is exactly what the ITS community seeks, hopefully using the Ann Arbor demonstration as evidence it should be done. That means every new car would be required to have such a radio in it (currently expected to cost $100 or so.) That's $1.5B per year in added expenses, though hopefully the price of the radios and associated gear drops with time. Once installed into all 250M US cars that's $25B at $100 but probably closer to $10B as it gets cheaper.

In order to get a legal mandate, it's necessary to demonstrate a compelling safety case. If V2V could prevent all blind intersection accidents -- which would be only after it reached very high penetration some decades from now -- that might be as many as 2,000 lives/year, so about $750K per life which is a quite reasonable value. But this is a big if. First, there are a lot of other ways to prevent those accidents, and that includes not just robocars but more advanced sensors in human driven cars and traffic lights.

Sensors on the cars don't have the network problem. If you buy a collision warning or braking system for your car, it provides value for you today. While it can't see a hidden car running a red light around a blind corner, it can brake for you (and the other car might have such braking too) and reduce the severity of the incident. And of course it will work in many other incidents.

I often quote what I call the first law of robocars "don't change the infrastructure." Mandating radios in everybody else's car is a huge infrastructure change, but there's another type of infrastructure change that might make sense here, namely sensors at intersections. Cameras are getting cheap and the cost of this could come down to be a tiny part of the cost of an intersection. An intersection camera that can detect somebody running a red light is able to make the light red-in-all-directions, and that benefits everybody in every car using that intersection from day one, not just cars that have installed new equipment. (Naturally the intersections could also transmit the alert over radio for cars that have got a radio.)

There are over 500,000 signalized intersections in the USA, so adding such sensors to all of them is also a multi-billion dollar project, though it's pretty reasonable if it's done during upgrades and new installs. While there are lots of intersections, the number of dangerous intersections with blind corners and a history of fatalities from intersection crashes is actually fairly small. All signals have an interface for the "conflict monitor" which prevents double-green. This interface can be used to turn the signal to all-flashing-red.

As a result, you meet that very important criteria I named above. You get value on your very first install of an intersection safety system. Value for all users of the intersection. Perhaps a mandate will speed things up, but in this case the cities buying more expensive traffic signal equipment due to the mandate would not resent paying money to get no present day value.

But it goes beyond this. If intersections start transmitting useful data -- not just safety warnings about people running lights, but simple reports on when the lights plan to change -- there is now an incentive for the people who use these intersections to want to get V2V/I2V radios in their cars. Not to talk to the few other cars out there, but to hear from the traffic lights. With this information they can time their arrival at lights to avoid stopping at reds. This produces a more comfortable ride and saves quite a lot of fuel in city driving. (This application can also be done over the wide-area cellular networks because it does not require low latency.)

Consider the following offering from some fraction of the traffic lights on your regular drives:

• They will send you an electronic warning if somebody is running the light in the other direction, which your car can use to hit the brakes for you even before you see the red light.
• They will tell you in advance when they will turn, so you can reduce speed rather than racing up to red lights and then breeze through.
• As a result, your car will also warn you or hit the brakes if you are about to run the red light.
• You can tell them you are coming, before they detect you, so that they can change ahead of time for you during low-traffic periods. (Right now you have to drive onto their buried loop sensor and wait for the light to change.) Even when they can see you they don't know you're turning until you get there.

While such sensors previously would have been considered expensive additions, it turns out that all the hardware needed for such functionality can be found in the old smartphones we are today throwing away by the millions. These contain cameras, processors, radios and run on low power. Because they are not designed for outdoor use, I am not suggesting we just glue a phone to the traffic lights. What this does mean is such sensors could be built at a low price from cheap, off-the-shelf parts. Even after the 10x increase in price that comes from government contractors, they would still be cheap.

This is just one basic alternate plan. However, a plan I think is even better, which involves embracing the opening of the spectrum and the use of the hundreds of millions of phones and other devices which would quickly have radios that work in that spectrum, comes in part two -- putting V2V into the mobile phone. Also look at part three -- using broadcast data.