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Robocars will make traffic worse before it gets better

October 25, 2017

Many websites paint a very positive picture of the robocar future. And it is positive, but far from perfect. One problem I worry about in the short term is the way robocars are going to make traffic worse before they get a chance to make it better.

The goal of all robocars is to make car travel more pleasant and convenient, and eventually cheaper. You can’t make something better and cheaper without increasing demand for it, and that means more traffic.

This is particularly true for the early-generation pre-robocar vehicles in the plans of many major automakers. One of the first products these companies have released is sometimes called the “traffic jam assist.” This is a self-driving system that only works at low speed in a traffic jam.

Turns out that’s easy to do, effectively a solved problem. Low speed is inherently easier, and the highway is a simple driving environment without pedestrians, cyclists, intersections or cars going the other way. When you are boxed in with other cars in a jam, all you have to do is go with the flow. The other cars tell you where you need to go. Sometimes it can be complex when you get to whatever is blocking the road to cause the jam, but handoff to a human at low speeds is also fairly doable.

These products will be widely available soon, and they will make traffic jams much more pleasant. Which means there might be more of them.

I don’t have a 9 to 5 job, so I avoid travel in rush hour when I can. If somebody suggests we meet somewhere at 9am, I try to push it to 9:30 or 10. If I had a traffic jam assist car, I would be more willing to take the meeting at 9. When on the way, if I encountered a traffic jam, I would just think, “Ah, I can get some email done.”

After the traffic jam assist systems, come the highway systems which allow you to take your eyes off the road for an extended time. They arrive pretty soon, too. These will encourage slightly longer commutes. That means more traffic, and also changes to real estate values. The corporate-run commuter buses from Google, Yahoo and many other tech companies in the SF Bay Area have already done that, making people decide they want to live in San Francisco and work an hour’s bus ride away in Silicon Valley. The buses don’t make traffic worse, but those doing this in private cars will.

Is it all doom?

Fortunately, some factors will counter a general trend to worse traffic, particularly as full real robocars arrive, the ones that can come unmanned to pick you up and drop you off.

  • As robocars reduce accident levels, that will reduce one of the major causes of traffic congestion.
  • Robocars don’t need to slow down and stare at accidents or other unusual things on the road, which also causes congestion.
  • Robocars won’t overcompensate on “sags” (dips) in the road. This overcompensation on sags is the cause of almost half the traffic congestion on Japanese highways
  • Robocars look like they’ll be mainly electric. That doesn’t do much about traffic, but it does help with emissions.
  • Short-haul “last mile” robocars can actually make the use of trains, buses and carpools vastly more convenient.
  • Having only a few cars which drive more regularly, even something as simple as a good quality adaptive cruise control, actually does a lot to reduce congestion.
  • The rise of single person half-width vehicles promises a capacity increase, since when two find one another on the road, they can share the lane.
  • While it won’t happen in the early days, eventually robocars will follow the car in front of them with a shorter gap if they have a faster reaction time. This increases highway capacity.
  • Early robocars won’t generate a lot of carpooling, but it will pick up fairly soon (see below.)

What not to worry about

There are a few nightmare situations people have talked about that probably won’t happen. Today, a lot of urban driving involves hunting for parking. If we do things right, robocars won’t ever hunt for parking. They (and you) will be able to make an online query for available space at the best price and go directly do it. But they’ll do that after they drop you off, and they don’t need to park super close to your destination the way you need to. To incorporate city spaces into this market, a technology upgrade will be needed, and that may take some time, but private spaces can get in the game quickly.

What also won’t happen is people telling their car to drive around rather than park, to save money. Operating a car today costs about $20/hour, which is vastly more than any hourly priced parking, so nobody is going to do that to save money unless there is literally no parking for many miles. (Yes, there are parking lots that cost more than $20, but that’s because they sell you many hours or a whole day and don’t want a lot of in and out traffic. Robocars will be the most polite parking customers around, hiding valet-style at the back of the lot and leaving when you tell them.)

Another common worry is that people will send their cars on long errands unmanned. That mom might take the car downtown, and send it all the way back for dad to do a later commute, then back to pickup the kids at school. While that’s not impossible, it’s actually not going to be the cheap or efficient thing to do. Thanks to robotaxis, we’re going to start thinking of cars as devices that wear out by the mile, not by the year, and all their costs will be by the mile except parking and $2 of financing per day. All this unmanned operation will almost double the cost of the car, and the use of robotic taxi services (Robocar Uber) will be a much better deal.

There will be empty car moves, of course. But it should not amount to more than 15% of total miles. In New York, taxis are vacant of a passenger for 38% of miles, but that’s because they cruise around all day looking for fares. When you only move when summoned, the rate is much better.

And then it gets better

After this “winter” of increased traffic congestion, the outlook gets better. Aside from the factors listed above, in the long term we get the potential for several big things to increase road capacity.

The earliest is dynamic carpooling, as you see with services like UberPool and LyftLines. After all, if you look at a rush-hour highway, you see that most of the seats going by are empty. Tools which can fill these seats can increase the capacity of the roads close to three times just with the cars that are moving today.

The next is advanced robocar transit. The ability to make an ad-hoc, on-demand transit system that combines vans and buses with last mile single person vehicles in theory allows almost arbitrary capacity on the roads. At peak hours, heavy use of vans and buses to carry people on the common segments of their routes could result in a 10-fold (or even more) increase in capacity, which is more than enough to handle our needs for decades to come.

Next after that is dynamic adaptation of roads. In a system where cities can change the direction of roads on demand, you can get more than a doubling of capacity when you combine it with repurposing of street parking. On key routes, street parking can be reserved only for robocars prior to rush hour, and then those cars can be told they must leave when rush hour begins. (Chances are they want to leave to serve passengers anyway.) Now your road has seriously increased capacity, and if it’s also converted to one-way in the peak direction, you could almost quadruple it.

The final step does not directly involve robocars, since all cars must have a smartphone and participate for it to work. This is the use of smart, internet based road metering. With complete metering, you never get more cars trying to use a road segment than it has capacity to handle, and so you very rarely get traffic congestion. You also don’t get induced demand that is greater than the capacity, solving the bane of transportation planners.

Brad Templeton, is an EFF board member, Singularity U faculty, a self-driving car consultant, and entrepreneur... read more

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