Why autonomous vehicles lead to more congestion

Cities are messy creations of sticks and stone that demand policies grounded in bricks and mortar to function and prosper. 

This is why urban leaders need to be pragmatic and why simple universal solutions to complex urban problems should make observers weary (remember Le Corbusier anyone?). At the moment, the autonomous vehicle (AV) is the silver bullet that is being held up as the spectacular solution for everything that is unpleasant and problematic in urban areas and it’s time to start questioning what practical benefits AVs really offers.

As any city dweller knows, urban areas are confined to geographical boundaries that can be traversed on a limited number of highways and streets. When a certain area is a great place to live, work or enjoy oneself the result is congestion since a lot of people want to get there at roughly the same time. Congestion is therefore an indelible part of life in great cities and a city can either deal with it by replacing attractive urban spaces by new roads and parking lots until neighborhoods are so unpleasant that no one wants to go there any longer, or by using existing highways and streets more efficiently in order to allow more people to get to and enjoy great urban spaces. If AVs are a silver bullet that solves the Gordian knot of congestion without debasing urbanity they would have to be extraordinarily efficient. Which begets the question – how efficient are AVs?

The short answer, not very.

A team of researchers at the Royal Institute of Technology in Stockholm, Sweden calculated what would happen if every single traditional car was replaced by a city-wide pool of AV taxis. That is, a wide-eyed radical thought experience and sharing-economy dream where no resident owned a personal car. The result, in one regard, was fantastic since this future Stockholm would do with 8 % as many automobiles as today. However, and this is a major disappointment, total traffic on the city’s roads would increase by 24 % since every single AV would spend a lot more time moving around than ordinary cars, usually empty, after leaving one rider and setting off across town to pick someone else up. Furthermore, most of this extra traffic would occur during peak hours, the very time when our roads are already jammed, since that’s when people want to move about.

Stockholm would only see reduced traffic if a second major behavioral shift occurred at the same time as all private vehicles were replaced by a city-wide AV carpool. This may not come as a major surprise – people had to start riding together. Does the word bus come to mind?

If you want to move a large number of commuters around a limited area during a short period of time people have to ride together in buses and trains, or opt for walking and biking – AVs or not.

Furthermore, there are reasons to believe that future traffic will be messier than today’s since people will be able to choose from a smorgasbord of interchangeable mobility solutions. There will be trains and tubes, automated buses, cars and pedicabs, scooters, ordinary bicycles, electrical bicycles and cargo bikes, Segways and solo-wheels, hover boards and more, all available for different segments of trips thanks to technology that makes it seamless to plan multimodal journeys. Smart phone apps enables switching between different transport-options depending on time-constraints, mood and variations in daily trip needs (are you going to run errands, stay out and meet friends, pick up kids or go straight home).

Given that a city will never have enough space to provide separated lanes for the plethora of transport alternatives outlined above, this complexity could lead to one very important development: that we start planning what neighborhood we want first and then let traffic adapt, since we can’t predict exactly how people will travel anyhow. The commuter is a highly flexible, though irritable, species that cleverly adapts to new obstacles and openings. In an urban world where we allow ourselves to accept its natural messiness, people will choose between many different transport options depending on what works best in a specific location. This mindset will provide a beneficial change compared to the current modus operandi where cities crudely extrapolate how many cars, trains and buses we will need in the future based on population growth, then build it and wait to see what kind of city that extra road space leads to.

Some of this future messy traffic will be AVs scurrying about; most won’t, since no mode of transport is the best choice for every occasion – and never will be. AVs will be a fun alternative among others, all with their specific pros and cons, but autonomous vehicles won’t be a silver bullet and we are fooling ourselves as long as we treat AVs like one and neglect the bigger picture.

Unless the real reason is promotional and the idea is to sell us more cars, then an AV-hype makes perfect sense.

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