Simple Machine: a mechanical device that changes the direction or magnitude of a force. In general, a simple machine can be defined as one of the simplest mechanisms that provide mechanical advantage (also called leverage). (Wikipedia definition for Simple Machine)

The reason autonomous, or driverless, cars are important is the same reason reducing greenhouse gas emissions from the transportation emissions is really hard – leverage (given the tomes already written about autonomous cars, I’m skipping the background tutorial). Electricity emissions reductions are RELATIVELY easier – there are a few large powerplants, a few large utilities, etc. Not so in the transportation section. In the US alone we have more than 250 million vehicles and more than 100,000 filling stations. And let’s not start on land use – with decisions being made by homeowners, and every jurisdiction from federal down to municipality influencing these decisions. Leverage is why fuel efficiency standards are so important, and why we spend so much time obsessing about transit routing.

Autonomous cars, if deployed en masse, under the right conditions, could provide significant leverage in reducing transportation emissions.  This is what makes them exciting, in principle; significant opportunities follow. To be clear up front – none of these benefits are guaranteed to occur, they are simply potential benefits that could follow assuming a lot of details get worked out.

1. Alternative fuel adoption: The big challenge with adoption of alternative fuels (whether we’re talking about biofuels, compressed natural gas, electricity, or hydrogen) has always been chickens and eggs: Consumers don’t want to buy something they can’t reliably refuel, filling stations don’t want to pay to install refueling if there are no customers. For those of us working on alternative fuels, a common mantra is: start with fleets. Fleet vehicles refuel at a central location. Plus they are driven many miles over their life. Alternative fuel vehicles often have high upfront costs, and low fuel costs. This is a problem for your typical consumer, but not for a fleet operator. Autonomous cars would essentially transfer maintenance of personal vehicles from individual car owners, to a central fleet service. That fleet operator would have a lot more motivation to adopt lower carbon fuels and vehicles (and could perhaps be more effectively motivated by policy and regulation). Leverage.

Source: Federal Transit Administration, “Public Transportation’s Role in Responding to Climate Change”

2. Smaller or shared cars: It is often assumed that transit is by definition preferable to driving with respect to emissions. It tends to be, but this advantage is not inherent. A fully occupied car (4 person carpool), actually competes quite well with most modes of transit in “average occupancy” mode (SEE ABOVE). Of course that is an unfair comparison – most car trips are pretty close to single occupancy, and a typical transit trip wins out even without full occupancy. But autonomous cars enable two scenarios that would encourage lower emissions for personal vehicles: the opportunity for shared trips, and the opportunity for much smaller, lighter, purpose-designed vehicles. Our current habit of leaving our cars unused 95% of the time and driving around in them at ¼ of their capacity is wasteful. But it would financially untenable for a company operating a fleet of cars. So in all likelihood, you’d see two things happen. Small 1-2 person vehicles would predominate (think Smart cars, but smaller) – they would cost less to operate, fuel efficient, and rival transit modes for GHG emissions. And larger vehicles would be reserved for picking up multiple passengers.

3. Operational efficiencies. Peloton Technology uses vehicle-to-vehicle communication to coordinate chained “pelotons” of over the road trucks. They claim aerodynamic benefits sufficient to reduce emissions by 10%.There is a whole subculture of “hypermilers”, who maximize gas mileage without the use of efficiency devices – only by altering driving techniques (e.g. slow acceleration, coasting, etc). Another term is “ecodriving”. According to Wikipedia, someone once got over 200 mpg in a Honda Insight. There is clearly huge potential for vehicles under autonomous control, coordinating with each other and programmed for fuel efficiency, to achieve dramatic reductions in fuel use, independent of other technological innovation.

4. Manufacturing emissions. Brendon Slotterback covers this topic nicely here, so I will only touch on it. Personal vehicles, I repeat, typically sit unused 95% of the time. If everyone used autonomous cars for all the trips now taken in personal vehicles, we would need 95% fewer vehicles. Now, most of the emissions from vehicles over their lifetime come from burning fuel. But still, this in not insignificant.

5. Motivation to drive less, or more? You can make the argument that autonomous cars could transform driving into an entirely variable cost (where you pay per mile), from mostly a fixed cost (i.e. most of the cost of driving is car ownership). That might motivate people to drive less, since every additional mile costs more. Some have made the induced demand argument – by making driving much cheaper and more convenient, people might drive more. Who knows the answer? Not me. A lot of it probably comes down to the pricing model, like a cell phone (unlimited minutes? pre-paid autonomous car cards?).

6. Reinforcing urban living? This is the big question. There are, of course, potential pluses. Imagine the space in the city that is devoted to parking that could be freed up for other uses if we needed 95% fewer cars, and the remaining 5-10% were in nearly constant motion (not parked). It could lower the cost of denser housing by eliminating the demand for large underground parking structures. It would eliminate some negatives of living in the core (parking is a hassle, traffic noise, congestion, etc). It could be transformative for urban air quality, etc. All that curbside parking could be turned into bike lanes, who knows? The possibilities are endless. Worth at least 5 more posts (but I’ll spare you).

On the other hand, if you don’t need to drive yourself on your long commute – maybe long commutes become more appealing. Also, what do autonomous cars do to the major transit investments we’re making? What does TOD mean anymore?

Source: “Transforming Personal Mobility”, Columbia Earth Institute report. http://sustainablemobility.ei.columbia.edu/files/2012/12/Transforming-Personal-Mobility-Jan-27-20132.pdf

In closing, I think some of these issues will come down to careful policy design. People I talk to in the industry tell me to expect commercial autonomous vehicles entering the market in 3-5 years. Let’s be pessimistic and say 10 (ignoring the products already on the market). Makes sense to start thinking it through…