The main reason we are excited about autonomous vehicles is that the massive reductions in fatalities they will bring about. Another reason to be excited is the potential of driverless cars to use far less fuel than driven cars. We think because most self driving cars will 1) be single passenger vehicles that will have less mass and require less fuel 2) self driving vehicles will be inherently safer and require less heavy safety features, further lightening the mass of the vehicle and its fuel consumption. 3) Autonomous vehicles may never have to slow down and stop at traffic lights, wasting energy in braking. In this line of thinking a recent article at published at e360.yale.edu made much the same point.

 Obviously, far fewer crashes means fewer fatalities and fewer traffic jams, but it also could mean a big change in car design and fuel consumption.

As originally pointed out by climate and energy scientist Amory Lovins, only about one percent of the energy in a gallon of gasoline goes to moving the driver forward. About 75 percent of the energy leaves the tailpipe as heat and almost all the rest is needed to move a 4,000-pound car. But the bulk of that 4,000 pounds is only there to keep the driver and passengers safe in the relatively unlikely event of a major crash. If that risk was reduced dramatically, 4,000 pounds might come down closer to 750 to 1,000 pounds.

Other technology, known as dedicated short range communications (DSRC), enables a car to tell an intersection that it is approaching. A computer system at the intersection would then be able to coordinate all the approaching cars — assuming they were self-driving cars — and funnel them through the crossroads without stopping. The reduction in crashes could be dramatic.

Of course, a massive reduction in fuel consumption means a lot less money is being paid to countries like Saudi Arabia that produce oil. This will cause a lot of political pain and a lot of political fallout as noted in Foreign Policy a couple of months ago.

The other potential improvement for fuel consumption that I didn’t see explicitly mentioned in the e360 article was the idea of platooning or road trains as being developed by Volvo in Europe. We did some rough back of the envelope calculations that if road trains were ubiquitous they could reduce fuel consumption in the US ~813,000 barrels of oil per day. When you think of combining road trains with super light, efficient vehicles that never have to stop at traffic lights, the fuel savings are immense.

Thanks to Paul Godsmark for putting these up on our Facebook page and apologies for not posting them sooner, both Mat and I have been swamped at work.