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What will autonomous cars mean for cities?

Google revealed this week that it is working on autonomous cars, and making a lot of progress. While it's what engineers call a nontrivial problem, making a car drive itself is ultimately just a matter of engineering, and will sooner or later become a reality.

Photo by dimic- on Flickr.

What will it mean for our cities? Will cars that drive themselves lead to more driving or less? More sprawl or more compact living?

On the one hand, long commutes will become more tolerable. Instead of suffering behind the wheel for hours, commuters who live far from their jobs will at least be able to get some work done or watch TV. This could make distant exurbs a bit more appealing and boost sprawl.

It will also probably cut down on commuter rail ridership, since some people choose rail over driving because they like not having to actually drive. However, even a small increase in vehicle volume will bring many freeways to a halt, making commuter rail more attractive time-wise, so it's not likely to have a large effect.

But the biggest change will be autonomous buses.

Today, buses have fairly high operating costs because of the labor involved. They're far more space-efficient than cars, but it's expensive to pay a driver. The biggest reason transit costs more to operate than highways is because with transit, you're paying a driver, but if you're driving your own car, you're doing the labor yourself.

That's a structural imbalance that puts transit at a budgetary disadvantage, until your car drives yourself and so can the bus. Suddenly, there's no difference.

Cities with self-driving trains, like Vancouver, can run far greater frequency at low ridership times like nights for a reasonable price. More vehicles makes transit more appealing.

Now, buses are often very infrequent or nonexistent at night, making them an unappealing mode for an evening trip, for example, unless you live right near a high-frequency, late night line. But what if the bus just drove itself every 5 minutes? Basically, it's like everything PRT promises, but without any guideways.

Or, better yet, what if it ran on demand? Then it's like a cheap taxi. And, in fact, buses, taxis, and car sharing will essentially merge into one mode.

Right now, each of those modes has advantages and disadvantages. Buses have the labor cost issue. Taxis have it even more, but are very convenient when available. Car sharing is great for certain types of trips, but you have to return the car to its starting point.

With autonomous vehicles, there will be no need to differentiate between vehicles that carry many people on fixed routes (buses), vehicles that carry few people on demand (taxis), and vehicles you can drive but are only in certain places (car sharing).

Instead, you'll simply be able to call a number or use a mobile app to book a trip. In urban areas, you'd go to a designated bus stop, or maybe pay more to get a custom pickup right where you are. A vehicle will show up at an assigned time, maybe picking up a few other people as well who are going to a similar destination, unless you want to buy a solo trip.

For more on how this could work, see Mark Gorton's Smart Para-Transit articles.

We'll need far fewer parking spaces in dense areas. Commuters from suburbs that take autonomous buses/taxis/paratransit vehicles/car sharing cars into the city won't need to park them. Instead, they can drive themselves around all day serving short-range trips as taxis. Others would live in the city full-time, and those might need overnight parking, but far less than we have today.

It will simply become far easier and cheaper to live in the city without a car. It won't really be like living without a car today. It will simply be like living with a car, without worrying about parking or paying nearly as much. Or, perhaps, it's like using car sharing, but with the guarantee that a car is always available and without having to worry about getting the car back in time.

Finally, assuming Google can perfect the software, streets will become much safer. The cars will be far better at avoiding crashes. Instead of most drivers speeding, turning improperly across bike lanes, and being distracted with texting or phone calls or the radio, the car will be "paying attention" at every moment (as long as its software isn't buggy!)

Governments and manufacturers will have to decide how to handle speed limits. Today, many localities set speed limits knowing most people speed. Will drivers be able to choose their speed, or will cars be required to travel the actual speed limit? If so, maybe we can finally rationalize all these limits and set them appropriately.

If governments set up autonomous car-only lanes on freeways or ban human-driven cars altogether once most cars drive themselves, traffic can move more efficiently. Right now, if a bunch of cars are stopped in traffic or at a light, each driver has to wait a few seconds after the car in front starts moving. With computers, the entire line of cars could simply start moving all at once.

The greater efficiency will allow existing freeways to carry more people than they do now, and since it'll be a lot easier to create carpools with Smart Para-Transit dispatching, even more if jurisdictions are willing to convert lanes to HOV. That could also accelerate sprawl, but the greater ease of urban living and lower need for parking will also facilitate infill development as well.

How else will cities change if cars can drive themselves?

David Alpert is the founder of Greater Greater Washington and its board president. He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He now lives with his wife and two children in Dupont Circle. 


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This would be a very protracted fight thanks to the Unions. Sadly.

by EJ on Oct 15, 2010 10:47 am • linkreport

I was just going to say the same thing as EJ. Unions will likely make buses and trains the last thing to go wholly autonomous once the tech is out there and proven with cars. They will be late adopters, in the techno parlance. :)

by Steve on Oct 15, 2010 11:05 am • linkreport

If all cars on highways were controlled by computers there would be fewer traffic jams and driving would be more appealing for many. Machines can manage merges and lane changes much more efficiently and at higher speeds. They would also never slow down to stare at an accident or linger at a green light while they argue with the kids.

by Nathan on Oct 15, 2010 11:09 am • linkreport

I'd like to see robot cars deal with Indian traffic.

And yes, litigation+unions+customer resistance will demand operators on buses for a long time. And which robot is going to stop fare jumpers?

by charlie on Oct 15, 2010 11:11 am • linkreport

The first thing I think of when I hear about robocars isn't unions - it's lawyers. Who's going to be held liable when a robocar malfunctions? Or when someone get hurt? The legal costs could put robocars at a significant economic disadvantage.

by Rob on Oct 15, 2010 11:25 am • linkreport

Autonomous police to deal with autonomous traffic accidents and autonomous EMS for pedestrian deaths.

by Redline SOS on Oct 15, 2010 11:33 am • linkreport

@charlie, you go proof of payment system instead of pay on board.

people will have to buy single ride tickets from the parking meters before boarding, or have a pass or electronic farecard.

by Michael Perkins on Oct 15, 2010 11:39 am • linkreport

"Right now, if a bunch of cars are stopped in traffic or at a light, each driver has to wait a few seconds after the car in front starts moving. With computers, the entire line of cars could simply start moving all at once."

I'm not sure that would be true. The required stopping distance increases with speed, and that is constant whether there is a human driver or not. I don't think it would be possible (or desireable) to have a line of cars going 40 MPH only separated by 2 feet.

by engrish_major on Oct 15, 2010 11:39 am • linkreport

who will be held responsible if a pedestrian is killed by an autonomously driven vehicle?

by dan on Oct 15, 2010 11:41 am • linkreport

I want an automated DeLorean.

by Bossi on Oct 15, 2010 11:44 am • linkreport

I would think that long before we have driverless cars, we will go through a period of computer assisted driving, roughly analogous to trains and planes today. The driver is still driving, but hazards are avoided by either driver or automatic decisions. Driving could become safer, though driver inattention might also become more commonplace, just as those who man trains and planes sometimes rely too much on their safety equipment.

Insurance could play a constructuve role. ALl this creates good data on a driver's true risk. Possibly also lower rates for those who do not make mistakes. Failure to yield to a pedestrian could ring a bell and add a calculated risk factor, so that at least some people would stay engaged in their driving even while it became safer. Companies might also provide lower rates for giving up some autonomy to violate traffic rules (albeit with manual over-ride to do so always there), but regardless the data would encourage it in a way that only one's conscious or a speed-cam do today.

by Jim Titus on Oct 15, 2010 11:47 am • linkreport

@charlie, or the system becomes cheap enough to operate that it's not worth the expense of a fare collection system to collect $0.25 per ride, so the local governments operate it for free.

by Michael Perkins on Oct 15, 2010 11:48 am • linkreport

This is about as pressing and urgent a question as, "What will happen to urban living when we all live on the moon?"

by Simon on Oct 15, 2010 11:49 am • linkreport

@engrish_major: The advantage of autonomous vehicles is the reaction time. It takes a human hundreds of milliseconds to brake in response to the car ahead braking, which necessitates a longer following distance to avoid rear-ending. A computer could react probably hundreds of times quicker, which is why you can have much shorter gaps between cars.

by dand on Oct 15, 2010 11:50 am • linkreport

@dand: I understand that. And the distances could be reduced. However, stopping distance is still greater at 15 MPH than at 5 MPH, regardless of the reaction time of the driver. Thus, at lights, each car will still have to wait for the requisite distance to be achieved before proceeding. And, I could even argue that on highways, distances would be even greater with autonomous cars, because I doubt that the average driver currently on 495 leaves a safe distance in front. Autonomous programs would probably allow for safe stopping distance, which might exceed the average distance between cars at this time.

by engrish_major on Oct 15, 2010 11:56 am • linkreport

@dand: unless you're strapping everyone down in five-point harnesses, you won't be able to exceed more than about 1/2 G for deceleration, which means a stopping distance of about 80 feet even with no reaction time. A reaction time of 0.1 second adds 5 feet to that.

by Michael Perkins on Oct 15, 2010 12:01 pm • linkreport

engrish_major: No, that's incorrect. The stopping distance is greater, but all the cars can start to brake at the same time. As long as the front car sees an obstacle within x feet, it can start braking, and the rear car can start braking at the same time.

Think of it this way. A semi pulling a trailer has 2 independent pieces, connected with a bar. (Some have more.) When it's at rest, the trailer is a certain distance from the cab. When it speeds up, they're still the same distance. The trailer doesn't need to back up 20 feet to maintain a stopping distance. Thet's because as soon as the cab hits the brakes, the trailer will start to slow down immediately.

In longer combo trucks, I think there are rear brakes that are separate, but connected by wire to the cab. As soon as the driver hits the brakes, the extra rear brakes kick in too. Again, this allows the whole unit to stop at once without needing stopping distance in between.

For the autonomous vehicles, think of them as a big long single vehicle. They start as one and stop as one. They can be any tiny distance apart, as long as they act as one. Maybe there will be a small delay based on the communications protocol, but that's miniscule.

Of course, this assumes that the communication is pretty darn reliable. You'd need to make sure there were backups. Maybe they communicate by Wi-Fi, and also each car talks to the next via infrared, giving two ways to keep in touch.

by David Alpert on Oct 15, 2010 12:04 pm • linkreport

A few points:
You write that "even a small increase in vehicle volume will bring many freeways to a halt, making commuter rail more attractive time-wise, so it's not likely to have a large effect." I disagree. Traffic is caused primarily by human error, not by volume. Autonomous cars could drive with virtually no space between them because there would be no sudden stopping. Imagine a line of cars with only inches between them moving at speeds unimaginable by today's standards. These cars would also be extremely energy efficient because of gains made from drafting and the ability to eliminate safety measures from cars and use light weight materials.

You also write that "right now, if a bunch of cars are stopped in traffic or at a light, each driver has to wait a few seconds after the car in front starts moving. With computers, the entire line of cars could simply start moving all at once." Here too, I think you are not seeing the full potential. There would be no need for lights at all. Fully automated cars could coordinate with cars coming on cross streets and adjust speeds so as to avoid a collision. There is no need to come to a full stop.

by David G. on Oct 15, 2010 12:05 pm • linkreport

@David G.: RE: "There would be no need for lights at all. Fully automated cars could coordinate with cars coming on cross streets and adjust speeds so as to avoid a collision. There is no need to come to a full stop."

What about pedestrians?

@David Alpert: That is a good point. I had not thought of the cars communicating with each other.

by engrish_major on Oct 15, 2010 12:12 pm • linkreport

@mperkins -- commie talk! Proof of payment! Free transit!

I see limited utility in driverless vehicles. Say industrial areas, or in airport. Highways-- maybe But really, once you introduce other drivers to the mix it will be very hard to control any computer.

I forget the number, but I think the average american driver an accident every 1 million miles -- given that may people go years or lifetime without an accident. 140K miles driven isn't very impressive.

by charlie on Oct 15, 2010 12:18 pm • linkreport

@english_major Re: What about pedestrians?

For dense urban centers, there would still need to be lights for this reason. In less densely populated areas with larger arteries, I think that lights could largely be eliminated. If a pedestrian were to cross one of these roads, autonomous cars would react accordingly.

by David G. on Oct 15, 2010 12:21 pm • linkreport

@engrish_major @dand In addition to the quicker reaction time, if you need to have more than a couple feet between the cars, you could always have the cars at the front accelerate faster than the ones at the back. That way, there would be more space between them, yet they would all start moving at the same time.

by imperator3733 on Oct 15, 2010 12:22 pm • linkreport

From the perspective of biking, I can say that I'm not sure if I'm totally enthused about the prospect of a computer giving me a right hook rather than a human. Which is better?

I think before we even think about using computers to drive our cars in congested urban areas, we have to figure out how to more intelligently provide facilities for all users.

We complain today about liability not being assigned to drivers for hitting peds and bikes, but how do you assign liability to a computer?

by neb on Oct 15, 2010 12:23 pm • linkreport

Oops, I forgot to refresh the page. Disregard my previous comment.

by imperator3733 on Oct 15, 2010 12:25 pm • linkreport

Well imagine a truly networked system. Automated electric buses whizzing down every suburban main road. Your phone, or other device, would know your destination and flag a passing bus down, and you would use it part of your journey. Your phone would let you off at the right stop, with minimal waiting time, to the next but that is going your way and so on.

In theory no need for a formal bus network and you route home from work could change every day depending on demand and the number of buses on the road. In practice buses would radiate out from heavy traffic generators along main roads, with neighbourhood circulators doing the final leg.

Unlikely in the near future, but it is more likely if there is no affordable alternative to gas powered private vehicles and electric ones remain expensive. It would allow people to still live in suburban cities, which with little traffic would be a breeze to commute from.

Sure changing vehicles 3 or times is nightmare now, but if it took less than a minute each time and you had no anxiety about missed connections probably not a problem. If it replace most peoples journeys then it would be fairly fast if there were also express options for longer distance routes.

by Rational Plan on Oct 15, 2010 12:27 pm • linkreport

With autonomous cars, this website couldn't complain about the media referring to a "car struck a pedestrian/cyclist" anymore.

by Fritz on Oct 15, 2010 12:46 pm • linkreport

@ Rational Plan

What happens to people who do not have phones or other capable device ?

by kk on Oct 15, 2010 12:54 pm • linkreport

@charlie proof of payment is how most of the world does light rail or high volume transit vehicles that board on the street, so it's not commie talk, it's reality.

Currently we charge about $1.00 on average for trips that cost $4. If we can drop the cost with lower operating cost, and at the same time get higher ridership by running more frequent vehicles, we might be able to get effective fares down to $0.25, and that's when it gets interesting, because you start getting to the point where it no longer makes sense to attempt to collect a quarter.

by Michael Perkins on Oct 15, 2010 12:55 pm • linkreport

The other way this could go is that we could keep the same or greater fares, keep the same sort of mediocre service, and the cities would be able to take away their subsidy based on lower operating costs.

I predict most American cities will choose the latter, and European cities will pick the former. In those cities, there will be four rush hour periods a day, as the cars that drive their owners to work then drive home for parking, and drive back to work in the afternoon to pick up their owners.

This assumes we aren't doing a lot more telecommuting, of course.

by Michael Perkins on Oct 15, 2010 1:13 pm • linkreport

Regarding fault or liability, its likely that the lawyer representing the first fatality will make a lot of money on appeals cases.

It will probably be decided similar to other cases involving defective products. The plaintiffs lawyer would have to prove that the product was defective in some way. Sort of like if the brakes malfunction on a car and it strikes a pedestrian.

I would expect the plaintiff to try to prove that the design or maintenance was faulty. Before such a car was offered for public sale, I would expect there to be NHTSA regulations regarding testing. There might even be a congressman working on a bill right now based on the Google story.

by Michael Perkins on Oct 15, 2010 1:25 pm • linkreport

I don't think it will ever happen. The main reason people like cars is the "independance" they feel. They might as well get on a mass transit route. All the supposed efficiency will be consumed by more cars till it reaches the same bottleneck point. Remember how free housewives where going to be after WWII with all those washing machines etc.? Everybody just filled their time with other stuff. Same as building more roads to relieve congestion, only to find that you have the same congestion in another 10 years. Then you've got the whole issue of hacking computers. It's like when everyone thought we'd all be working remotely because the computer made it possible. What if you want to randomly stop and photograph a nice victorian for the next project you've got coming up? I just don't see it.

by Thayer-D on Oct 15, 2010 1:44 pm • linkreport

I'm going to go out on a limb here: there's no chance in Hell that autonomous vehicles are going to be legal to operate in DC anytime soon. A majority of DC voters will fight that to the bitter end.

The only automated function that cars operated in DC will have in the next 5-10 years will be speed-limiters.

by oboe on Oct 15, 2010 2:01 pm • linkreport

@KK, in 20 or 30 years time who will be without a personal data device. You could have a simple electronic transit payment data device. By that time it would be low cost or an app for your phone. It only has to know where you are ans where you want to go. The transit system it itself would handle your route planning and notifying vehicles who it has to pick up and let off, and send reminders to peoples devices.

by Rational Plan on Oct 15, 2010 2:02 pm • linkreport

@ Rational Plan

There are lots of people without electronic devices around the global. I know many people who choose to not have cell phones or mp3 players because they are of no use to them and can do all there business without them or in the case of the cell phone without paying a monthly fee.

So what about people from foreign countries or people who choose to not have them; what if someone normally doesn't take the transit and has to due to emergency.

by kk on Oct 15, 2010 7:35 pm • linkreport

My predictions of what will happen if automated cars really take off (and assuming that we figure out how to power them - i.e. electric cars powered by renewable energy):

- Automated freeways become the dominant method of transportation due to vastly improved safety, improved capacity due to vehicles travelling closer together, higher maximum speeds of up to 200km/h (when there is no traffic congestion), and high redundancy.
- Suburban sprawl continues its march unabated. Automated cars and buses will make long commutes more tolerable, but of course the trend of jobs moving to the suburbs will continue.
- Traditional non-car oriented walkable cities will decline but remain popular with a small minority of the population. On the other hand, many newer suburbs will begin to resemble traditional walkable cities in some ways, while remaining highly accessible by car as well.
- There is a proliferation of cheap robotic taxis which reduce the need to own a car and the need for parking. Personally owned cars remain popular largely as a status symbol, despite the high cost of owning a car and parking, but fewer people feel the need to own one.
- Public transit in big cities mostly takes the form of large numbers of robotic buses, which are able to run at much lower cost thanks to elimination of the human driver. Rail disappears except perhaps in the very largest, high density cities because a lane of robotic buses can carry more passengers than a bus lane, because buses have better redundancy (a closure of a freeway causes less disruption than a closure of a subway line), and because there is less need for transfers. High speed/intercity rail disappears completely being inefficient and costly compared to robotic buses and cars. Taxis act as feeders to buses, with commuters often transferring to and from taxis at the end of their trips to access areas not accessible by bus.
- Public transit in small cities and rural areas declines (operates only on congested routes at rush hour) or disappears completely. Public transit at low-demand times of day (e.g. late at night in low density suburbs where there is little car traffic) disappears and is replaced by taxis.
- Automated trucks proliferate and displace freight rail. The cost of delivery services decline, so online shopping becomes much more popular and much faster (e.g. order groceries online, have them appear within 1 hour), and retail mostly disappears.

by Andrew on Oct 16, 2010 12:10 am • linkreport

It looks like Google has reinvented PRT. These vehicles require a human for backup. If an emergency occurs, the human has to take over. The problem is that by relieving the human of responsibility for driving the car, he will find other things to do. The result will be things like crashes with other cars, pedestrians, and stationary objects, especially when the cars first begin to operate. The only way these hazards can be avoided is by using dedicated rights of way. In other words, PRT.

The same problem appears in commercial aviation. Aircraft have become so heavily automated that pilots have little to do. Unless they are given something to do to keep them alert and aware of their surroundings, the result is crashes and separation violations resulting from inattention.

The moral of the story is that all automated forms of transport have to have dedicated rights of way and centralized human monitoring for safety.

by Chuck Coleman on Oct 16, 2010 9:43 am • linkreport

This posting is pure fantasy. To say that Google is making "great progress" seems fair, yet we aren't going to see driverless vehicles on roads (except maybe for specially constructed busways or otherwise reserved purely for such vehicles) in any foreseeable future. A hundred years from now, who knows? But not in a scenario or timeframe that has actual relevance to today's problems.

What we might see is more automation that helps drivers (who won't go away) avoid many kinds of accidents. That might be an interesting topic to discuss. But the idea of doing away with drivers and cutting costs is pure fantasy.

by David desJardins on Oct 16, 2010 3:27 pm • linkreport

I think one result will be that people won't have an expectation of privacy when utilizing taxi-like robot cars they don't own, perhaps operated by private companies. Also, public roads and the idea of public space will be obsolete if people can be tracked, charged for the use of facilities, and monitored by technology. Today we take for granted being able to have the freedom to choose any destination and simply go there-I can get in my car and drive it to any random place so long as I am on a public street. And I can drive my car, walk, or ride a unicycle while dressed as Spongebob Squarepants as I please in this public space, unless there is some valid, justifiable rule that says I can't.

But I can imagine that in one of these taxi-like vehicles on private roadways(all streets and roads can be privatized down to inch if its possible to track and charge the users of them), you have no intrinsic rights, to be anywhere or do anything or say anything, whatsoever without consent of the property owner(vehicle, road, or all-in-one corporate

This will be an interesting thing on the magnitude of when the Supreme Court had to address the issue of interstate commerce back in the 19th century,

by TXSteveW on Oct 16, 2010 4:28 pm • linkreport

How about an "automated lane" on the freeway? Imagine being able to put 80% of highway traffic in a single lane (because of the reduced response time and end of "butterfly effect" stops & starts). We would never have to expand a single highway because car spacing would be so much more efficient.

by Amanda on Oct 16, 2010 9:46 pm • linkreport

@Amanda: How about an "automated lane" on the freeway?

This seems to me still a bit beyond the bounds of feasibility in any foreseeable future, if you are talking about a system that will run cars at a much higher speed than would be safe with human drivers. What happens when debris is in the road? Or when a car in a neighboring lane drifts into the lane? Or the car in front of you blows a tire? I don't think the potential density gains are as large as you imagine---cars still need a buffer for stopping even if automated---and the potential for relatively rare but high profile accidents seems high.

by David desJardins on Oct 16, 2010 9:52 pm • linkreport

I figure that cities will be better off. Unlike what others have said, I don't see why traditional walkable cities would "decline".

Maybe some cities where people are forced to live in a uncomfortably dense, overpriced area they don't really have any attachment or pride in only because of transportation to where they work, that will happen.

But I think actually, depending on the formula in which these cars work, the most optimal places will be moderately dense and diverse, decentralized but also mixed-use.

Remember the issues with bike sharing and how bikes end up scattered around outer neighborhoods? Robotaxis may drive themselves back but that is not as efficient, or profitable for the operating companies, as if those cars could be moving people in both directions.

People will want to live in places and be subscribers of the robotaxi companies which can provide the fastest trips and least wait times and are also the cheapest. These will be the places where movement is the most efficient(riders on both ends, short trips due to density), and the cheapest will be places where you can have the lowest ratio of shared vehicles to users thanks to the first two factors.

Using a robocar in suburban Atlanta may cost more and take longer than in Portland. Of course, it may cost more in New York too.

Another idea is that with tons of data from knowing all the customer data is that new communities can be planned optimally with little guess work.

by TXSteveW on Oct 17, 2010 1:06 pm • linkreport

Some of the motivation for buying a car is the supposed joy of driving it -- at least that seems to be what the commericals are pitching from time to time.

If that goes away, and people essentially become passive passengers in a small bus, will cars be as popular? Just asking.

by John Schneider on Nov 1, 2010 10:00 am • linkreport

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