No, Giant Shared Ubers Aren’t About to Solve City Traffic Problems

Would sharing for-hire trips cut traffic or lead more people to hire cars to get around? Photo:  Ad Meskins, Creative Commons license.
Would sharing for-hire trips cut traffic or lead more people to hire cars to get around? Photo: Ad Meskins, Creative Commons license.

A new study on shared vehicles by MIT researchers was tailor-made for internet news. Using taxi trip information, researchers developed an algorithm for pooling customers headed in similar directions. They concluded that ride-hailing services could replace 85 percent of New York City’s taxis — if up to 10 passengers shared each vehicle.

Online media gobbled it up.

But on Twitter, many people deflated the hype:

Economist Joe Cortright at City Observatory has a detailed analysis of the problems with the MIT projections. The math is sound, says Cortright, but the assumptions are not:

Autonomous vehicle designers may be using LIDAR, imaging, vehicle-to-vehicle communication and prodigious computing power, but down deep they’re still engineers, and they’ve apparently given no thought whatsoever to induced demand. Just as highway engineers have assumed that there’s a fixed demand for travel and that highways need to be sized accordingly, and ignored the effect of new capacity on in stimulating added travel, the MIT study assumed that the current level of taxi use exactly captures future travel demand. It’s worth noting that the demand for taxis is limited, in large part, because New York City has long regulated the number of licensed cabs via its medallion system.

There’s no reason to believe the demand for 10- and 4 passenger vehicles would be restricted to just those who currently patronize cabs. Taxis handle about 360,000 rides in the Manhattan daily. About 2.8 million travel to or from Manhattan by public transit.  If their were suddenly a viable on-street ride sharing option — especially if it were cheaper — the system could have much more demand — which could swamp the congestion reducing benefits.

The big urban transportation challenge is not simply optimizing a pre-determined set of trips, its coping with the complex feedback loops that produce a fundamental law of road congestion. This study glosses over that inconvenient truth.

Cortright’s full post has more insights and is worth your time.

What we’re also reading today: The Frontier Group shares revised national traffic figures that show driving mileage is not increasing as much as previously reported. And Greater Greater Washington says abandoned office buildings hold promise as sites for affordable housing in D.C.

  • Sri Napasaran

    I think Uber is shooting itself in the foot. Think about it – Uber has 45,000-50,000 cars in New York City. If such a huge number of Uber cars hasn’t solved this problem already then the whole approach is wrong. Adding more Uber cars will not help the City and only make already horrible traffic conditions in Manhattan worse.

  • kevd

    Are those the same MIT brainiacs who decided to model an AI intersection in the middle of Boston with Zero pedestrians and cyclists?

  • adam

    Cycling will not be needed in the future when you can hop on an autonomous bike or vehicle and reach your destination in rapid speed. Driving will be illegal on major city streets and perhaps cycling too. It would just seem absurd to drive a device that can kill so easily, or be killed so recklessly when there will be a 0% fatality rate caused by autonomous vehicles.

    City/street planning folks seem very scared of autonomous vehicles because it removes the fantasy utopia of improved city transit with less cars. Autonomous vehicles will remove the needs for BRT and other currently good ideas.

  • adam

    The more cars on the road the less money for Uber drivers, so their numbers will never be so high as to cause entire weekend traffic jams like in China. When Uber and others develop autonomous vehicles the problems you note will be no more.

    If you were to be discussing self-driving vehicles, the fundamental variable you are precluding is the human element. Autonomous vehicles will fundamentally remove that element. Our roads are designed in such a manner that factors in and controls human decision making. Autonomous vehicles will communicate with each other and the road, so the human factors that limit speeds and volume on roads will greatly increase. The exact number of self-driving cars will be figured out, it won’t be an incredibly high number because that won’t be needed, as the MIT study showed (with human drivers). Traffic will be a breeze, always.

  • kevd

    Yeah. Sure. And we’ll all wear metallic unitards.

  • murphstahoe

    If there is a zero fatality rate from autonomous vehicles, then cycling becomes safe. And even a driverless car is much more expensive than riding a bike. Autonomous cars will increase cycling

  • Joe R.

    What about riding for fun? And the reason why city/street planning people dislike the idea of autonomous vehicles replacing rapid transit is because it’s unrealistic and creates more problems than it solves. Some autonomous vehicles can be a good thing, provided they are priced in line with what taxis or car services currently cost so they function basically as “luxury transit”. Autonomous vehicles could well mean half or a third of the number of taxis on the street serving the same number of people. Ditto for delivery trucks which could run their routes more efficiently. Less traffic, plus programming the vehicles to automatically yield to bikes and pedestrians, would make walking or biking much more pleasant and much faster, as well as close to 100% safe. This in turn could result in a lot more trips being done by bike or on foot.

    Same reasoning applies to buses. Autonomous buses on fixed or semi-fixed routes could run much faster than now, making them a viable means to get around even for those who currently drive. And of course autonomous vehicles can park themselves anywhere where not in use at off hours, perhaps using one or more lanes on local highways for parking. That should remove the need for curbside parking altogether. It’ll probably also reduce the need for parking lots by over 90%. Everything here is good because the end result is more mobility, more pleasant streets with far less traffic, the ability to walk or bike unimpeded in perfect safety.

    What we don’t want are many small autonomous vehicles which are so inexpensive to use that they replace conventional public transit altogether and form a continual stream of vehicles 24 hours a day on urban surface streets. That idea can’t accommodate pedestrians or cyclists, nor would such an environment be pleasant for them. Trying to accommodate them would severely delay the autonomous vehicles, making the whole idea rather pointless since travel times might be no better than in my first scenario. Or in other words, it’ll boil down to what we have now, a deliberate choice to prioritize motor vehicle users over everyone else. And the idea I should need to pay and wait for a vehicle to go 4 blocks to the local grocery because I’m prohibited from walking there for the convenience of motor traffic is patently ridiculous.

    The MIT model is probably a lot more applicable to outer ring suburbs where few people can walk or bike to their destinations. There it should preclude the need to own a private automobile but still allow people the same or better mobility than they enjoy now. But in cities what has worked for ages is allowing people to get around under their own power and freely mix with other people. Turning every street into essentially a surface level highway is counter to that goal, and I will oppose it vehemently.

    What may work in some cities which are too spread out for conventional mass transit to work well is using autonomous PRT (personal rapid transit). The vehicle could pick you up at your destination, drive at a slow, safe speed, yielding to pedestrians or cyclists, to arrive at a grade-separated guideway where it can complete most of the journey at much higher speeds. Then it gets off the guideline and takes the user to their final destination. Or put more succinctly, if we want autonomous vehicles to move rapidly around cities, then they need grade separation like any other form of rapidly moving vehicle does now. The expense of that in turn would mean these vehicles basically function as luxury transit.

  • Joe R.

    Don’t laugh—some types of metals, like silver, have antimicrobial properties. And I would personally like the idea if we lived in a world where superficial appearances or projections of wealth are frowned upon, such that most people voluntarily chose to wear some updated, metallic version of Mao suits or unitards, or something fairly plain and utilitarian. The fashion industry makes people waste billions of dollars a year trying to hit an ever moving target. And don’t get me started on heels. Just looking at women willingly subjecting themselves to eventual spinal problems solely for superficial reasons makes me cringe. I don’t even find those wearing them “sexy”, which I assume is their intended effect on males.

  • Charlotte

    There would still be a space problem in this case- a single passenger in their own car (or an Uber or taxi) is taking up at least 25 square feet of road space per passenger. A passenger on a bus that can convey dozens of people who are going in the same direction to similar destinations take up far less space. Unless all these driverless vehicles will be phone-booth sized compartments (as some prototypes have shown), then traffic will not just disappear.
    Transit is generally good for cities because is is space-efficient, not necessarily always time-efficient. But because of traffic, sometimes transit with dedicated guideway (e.g. rail, BRT) is also more time efficient.

  • Frank Kotter

    I don’t know if you are saying this toungue in cheek or not but I don’t currently ride a bike and walk because I ‘need to’ – I do because I want to. Also, my bike riding endangers no one and the only thing endangering me are motorist. So sure, let’s try out AVs. You might be right. However, assuming that this will eliminate walking and cycling because it is no longer needed or safe is dubious.

    Also, I’m not quite sure why you see AVs as a better solution than a vast improvement in public transit infrastructure and services. Why?

  • Joe R.

    There’s also the fact that walking and biking are essentially “free”. People either won’t want to, or won’t be able to, pay for AV transit for a trip they can easily walk or bike. Also, who wants to wait for a vehicle to arrive for a trip of a few blocks? AVs can be useful in lots of situations, but the notion they can replace biking or walking is patently ridiculous.

  • Frank Kotter

    *Misposted my response to you above*

  • Frank Kotter

    When you remove the driver and don’t demand extensive fees for registration and use the cost to keep AVs driving around cities (not having to store them anywhere) is basically zero. So what will be the cost which will effect this balance you speak of? The economic factors will basically DEMAND as many vehicles as possible as providers will need to have cars as close to a hail at any one time as possible to stay competitive.

    Yes, you could do it with regulation, however, that is not the direction the American people are presently inclined to support.

  • ChicagoCyclist

    Fact is: when it comes to autonomous vehicles, we simply do not — and cannot — know or foresee for all the ‘consequences’ — i.e. how the technology will really, ultimately pan out. To think that you understand what will happen, what will be, in this realm, is plain old, tragedy-inducing HUBRIS (look it up). We need to devise a way to test, muddle along, adapt AV technology — using reason, data, and emergent/provisional ‘truth’ as our guides — and having the hard, uncompromising and uncompromise-able guiding principles of sustainability, equity, health, and transportation that provides better access for all, and helps to create better cities and metropolitan area for everyone (old, young, mobility-disabled, moms with strollers, low-income folks — everyone!). Pace technology of all kind, bicycling, walking, and public transportation will remain the primary means of achieving this equitable, sustainable access and mobility in urbanized areas. This ‘adaptive’, ‘flexible’ approach involves — as we test/muddle/adapt — government and government policies STANDING STRONG and being BRAVE (i.e. exhibiting political will) in the face of powerful transportation and technology industry interests that have invested or plan to invest in one way or another of making money (i.e. ‘corporate’ interests). Governments in this country, alas, have not shown themselves good at bravery, strength, acting according to reason, data, etc. Government and elected officials have, on the contrary, shown that they are highly prone to ‘caving in’ to special interests (money, corporations) that are willing to lobby (i.e. bribe) officials to gain an outcome that is beneficial to their own profits and not to society as a whole.

  • AnoNYC

    Autonomous vehicles that can operate flawlessly on city streets are still several decades away. The idea that they will traverse city streets at high speed is unlikely for some time. The average American keeps a vehicle for what, 10 years. And shared rides are more realistically going to be commonplace in dense areas. Automakers are not even going to be mandate to standardize basic collision avoidance in the USA until 2022.

    More realistically, cities are going to invest in more mass transit, bicycling and pedestrianization for most of our lifetimes. Even then, autonomous buses and subways are more efficient people movers in confined cities.

  • Christina

    The way they can help the traffic problem is getting off the road. I use the taxi app E-HAIL (www.goehail.com) same convenience but real drivers.

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