Vehicle automation can drastically reduce the number of road fatalities, given that 90% of them are caused by human errors. Even if accidents involving autonomous vehicles (AVs) have happened and will certainly occur in the future, expected safety benefits will be significant. However, depending on whether they are regulated, autonomous vehicles could either worsen congestion and emissions (traffic hell) or decrease them (traffic heaven).
In the hell scenario, self-driving cars remain privately owned, and run on internal combustion engine. Because of the convenience of autonomous cars (you don’t need to find a parking spot and the vehicle is always available) vehicle kilometres increase and so do congestion, noise levels, and emissions. There’s less space available for other modes or for social activities.
On the opposite, in the autonomous heaven scenario, self-driving cars run on renewable-based electricity and are available on demand. Autonomous cars are part of shared fleets people can subscribe to in order to book a ride on an as-needed basis. They’re charged less if they share their rides with other people.
Vehicle utilisation becomes much more efficient as these vehicles are shared and sometimes pooled. In this scenario, there are up to 90% fewer vehicles on the road, meaning less road space is needed, sidewalks and bike lanes get bigger. There’s no need for many parking spaces, which frees up (expensive) city space for housing or social activities. Congestion and road transport pollution are eliminated.
Ultimately, the outcome will depend on the policy framework, and most importantly on whether autonomous vehicles are electric and shared.
In parallel, rapid development of app-based on demand mobility services such as ride sharing have great potential to theoretically reduce car ownership and emissions, as the International Transport Forum has shown.
But according to US city data available in San Francisco or Boston, ride sharing services like Uber are currently adding kilometers to the road, leading to more congestion and pollution.
For instance, in San Francisco, Uber and Lyft are the biggest contributor to the growing traffic congestion. Researchers found that between 2010 and 2016, weekday vehicle hours of delay increased by 62% compared to 22% in a counterfactual 2016 scenario without these services available.
In Massachusetts, the department of public utilities estimated that ride sharing services had a net carbon footprint of nearly 100,000 tons of CO2 equivalent in 2018.
This data stresses the importance to accelerate the transition of ride sharing services to zero-emission to limit their negative impacts on air pollution, which should be a prerequisite to their operations, at least in big European cities within the next few years.
Shared mobility isn’t only limited to cars, but also include lighter transport modes such as micromobillity. Since Lime and Bird first started to offer on-demand, shared e-scooters in the US, the number of e-scooter sharing companies has quickly multiplied, offering their services in many European cities. As flexible mobility solutions similar to (e)-bike sharing, they can offer first and last mile connections in dense urban areas.
However first usage data from e-scooters indicate that these micro-mobility options are barely replacing private cars and are mostly substituting trips that would have been made walking, cycling, or using public transport. There are also environmental concerns about the scooters’ sustainability and longevity.
Some key principles can help maximise the benefits from autonomous and shared transport: On-demand, shared transport solutions should be integrated with the existing public transport network, making public transport more flexible and attractive. This implies appropriate data sharing between different mobility providers.
Given their potential impact on increasing the number of kilometers driven, all AVs should only be electric and available on-demand, as part of fleets.
The roll-out of micromobility vehicles shall ensure a matching supply and demand as well as safe usage conditions, including clear parking rules.
In parallel, regulating road and curb use to favour shared modes over private mobility (e.g. congestion charging and low and zero emission zones, bike lanes, exclusive parking rights for shared vehicles) will encourage people to share.