Will autonomous vehicles really put an end to traffic congestion?

Technology and Business

Alice Salter

Alice Salter



In this article, we take a closer look at AVs’ impact on traffic, and ask:

  • How do autonomous vehicles impact traffic flow?
  • Will ridesharing make congestion better, or worse?
  • Could adapted road systems reduce traffic?


The closer we come to realising our ‘driverless dream’, it seems the number of issues autonomous vehicles (AVs) are expected to solve is increasing. With the technology promising everything from safer travel, through to dramatically expanded opportunities for work, entertainment and socialising on the go, we’re anticipating widespread change with the arrival of AVs.


Naturally, road accidents are often cited as the greatest problem driverless technology will solve, but safety itself should be a guarantee of a fully functioning and publicly released AV. How this technology will impact our experience of travel, therefore, may be a more interesting question. With two billion cars expected to share our roads across the globe by 2035 and congestion a near constant concern for drivers, could self-driving vehicles make our experience of travel one free of traffic, gridlock and delays?



Source: Unsplash

Changing traffic flow


According to a 2019 study from the University of Cambridge, driverless cars could improve overall traffic flow by up to 35%. Key to that improvement, though, is AVs’ ability to work together. As co-author Nicholas Hyldmar notes, “If different automotive manufacturers are all developing their own autonomous cars with their own software, those cars all need to communicate with each other effectively.” Not just that, they need to be able to platoon with ease.


We’ve spoken before about how platooning, where self-driving vehicles drive more closely to each other with safety ensured via constant communication, will free up space on our roads. In the pursuit of free-flowing traffic, this behaviour is a major plus, however it requires a significant number of AVs on the road to make real impact and we’re just not there yet.


Still, Alexandre Bayen, of University of California, believes even single vehicles can reduce congestion. His most recent studies show that just one autonomous vehicle can eliminate traffic by subtly moderating the speed of human-driven vehicles in a small area, while achieving a mix of 5-10% AVs results in better management of even complex environments. Unfortunately, though, this may not be a natural result of simply increasing volume of AVs on the road. To achieve these results, manufacturers will need to actively consider their driverless technology as a traffic management system, integrating the needed tools for effective V2V communication and algorithms designed to reduce congestion. Right now, it doesn’t look like the biggest priority. congestion

Will a shared model reduce potential benefits?


Though there is plenty of promise that self-driving vehicles can reduce congestion in cities, a lot still depends on how the vehicles themselves are rolled out. A 2019 study from University of Adelaide, for example, suggests the advent of driverless may have a negative impact on shared and public transport, increasing the number of vehicles on the road and ultimately adding to congestion.


The ease of driverless travel, and the convenience of sending empty AVs on errands, may add to this trend. A 2018 study in the San Francisco Bay area offered subjects a free chauffeur-driven vehicle for a week to mimic the ease of travel an AV promises. The significance of this study lies in human behaviour. Without the burden of actually driving, subjects travelled more miles in the vehicle and a substantial number of trips were made on a ‘zero-occupancy’ basis.


Similar trends may arise should the much discussed ‘robotaxi’ model take precedence. While shared travel offers convenience and cost-efficiency, it requires additional ‘zero-occupancy’ miles to driven as each vehicle must make its way to its passenger, rather than the other way around. Researchers at Singapore-MIT Alliance for Research and Technology investigated this just last year, and discovered that high volumes of ridesharing vehicles increased road congestion in both intensity and duration.


Despite these issues, there remains hope for the shared model. Moving beyond ridesharing alone to an intermodal approach where AVs share space with public transport systems, current travel routes will undoubtedly change and so improve traffic flow. With the help of first/last-mile vehicles, like EasyMile’s people mover, more could utilise central public transport systems with ease, reducing the number of vehicles moving through more built-up areas like cities.


Though stopping for drop-offs causes delays and an increased volume of vehicles on the road will undoubtedly have an impact, suggests the more constant rate of speed achieved by AVs can have quite an incredible impact on traffic flow more broadly. Even with the issues identified here, self-driving vehicles can ultimately reduce congestion through the influence they exert over people, reducing the chain reactions which so often hinder traffic flow and providing entirely new, and more efficient, systems of travel.



Adapted road systems


Taking this one step further, some suggest the key to both reducing congestion and successfully launching self-driving tech is the separation of machine- and human-driven vehicles. Michigan in the US, for example, is set to create separate lanes for autonomous vehicles, ultimately creating more space on our roads.


Though such ‘driverless corridors’ may reduce congestion, many suggest it comes at a cost. Not only does this approach require mass expansion of roadways, it could easily lead to congestion-free travel becoming something which is bought, rather than achieved for all. In fact, here at 2025AD we’ve already hypothesised how a mix of subscription autonomous travel and dedicated driverless corridors could create an disparity for travellers.


It's clear this question is a complex one and, as yet, no single route to congestion-free travel has emerged. Based on existing research, it seems most sensible to agree with Lance Eliot, an expert on artificial intelligence and machine learning who writes for Forbes, “It’s quite unlikely that self-driving cars will bring us a congestion-free nirvana, certainly not in the foreseeable future.”

Still, there remains hope that driverless technology, and increased on-road communication which is expected to grow alongside it, will have a positive influence on traffic flow through our cities. Alone it may not be the perfect solution, but it is certainly moving in the right direction.



What do you think? Will driverless vehicles reduce congestion? Or will the convenience of AV travel just put more cars on the road? Share your thoughts in the comments below!


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