The idea of “road trains”, a group of cars using advanced technology to form a caravan of cars driven semi-autonomously, arose from two different sources this week.

The (in)famous Antiplanner, Randall O’Toole, touts road trains as a congestion-relief solution superior to rail building in his new book, Gridlock: Why We’re Stuck in Traffic and What to Do About It.  He says building new roads is “politically difficult” and that new passenger rail construction “rarely makes economic sense”.  Enter road trains.  They can increase the capacity of existing road networks, according to O’Toole.  He claims this technology can increase highway lane capacity by 200% to 400%.

The second source is the EU’s Safe Roads and Trains for the Environment initiative, which is actually implementing the road train concept.  Cars signal their destination wirelessly to road trains already on the road, and then technology takes over to group the cars and control steering, braking and navigation.  The lead vehicle, perhaps a bus or truck driven by a more experienced driver, monitors the status of the road train.  When you approach your exit, your car leaves the train and you resume manual control.  The EU work suggests fuel consumption for the vehicles behind the lead vehicle can be cut by 20%.

This approach avoids the large costs associated with embedding sensors in roadways to guide vehicles, and instead relies on technology within each vehicle (collision avoidance, navigation system, automated braking and steering).  O’Toole puts the cost of this technology at between $1,000 and $10,000 per vehicle.  I’m interested to see if his book includes a calculation of how much transit, bike lanes or other alternatives you could buy for the cost of installing this technology in all vehicles.

The benefits of this technology are numerous if it can be implemented:

• A reduction in fuel consumption.
• Providing the comfort and independence of an SOV with some of the efficiencies of transit.
• Not having to drive.  Giving car passengers back their driving time, for leisure or productivity, would be a huge gain.

I see some downsides though:

• Increasing capacity on highways doesn’t equal increased capacity on city streets.  This technology is perfect if every destination is adjacent to a freeway off-ramp.  However, greatly increasing the capacity of highways while keeping the city streets (where drivers still have to use their puny human brains to drive) the same seems like it would equal chaos.
• Equity.  This “solution” to congestion puts all of the costs onto the car owner.  If you think everyone should have equal access to the transportation system (and you plan your land use so that a car is almost essential), you should think about how to make this technology (which probably means a new car) affordable to everyone.  O’Toole suggests “transportation vouchers”, an idea based on people making personal choices about the best transportation mode (although he really thinks there shouldn’t be any choice, the car is king).  Not a bad idea necessarily, but I would suggest combining it with a true mileage tax to raise the necessary revenue.  I assume O’Toole supports this idea since he says in his book review that he does not support any government subsidy to transportation.
• Different cars and maintenance regimes = crashes?  In all the articles about road trains, I haven’t seen any discussion about how to handle the different capabilities of individual cars.  Some cars have much better brakes than others.  Some cars can accelerate more quickly.  People maintain their cars differently (meaning they do less maintenance).  Can the technology compensate for the different capabilities of each car?  Does each car “know” the distance required to stop based on its components and the condition of its parts?  Bringing this technology to the real world means accommodating all kinds of cars, of varying ages, types and capabilities.  Unless of course this advantage is made available only to those who are able to afford the newest and best vehicles, or we move to a uniform, government-regulated and maintained pod-car.