Services of electric and self-driving vehicles have the potential to make mobility in cities more efficient and demand oriented. They are expected to improve safety and traffic flow, and reduce the space needed for roads.

But how can planners and decision-makers ensure that these positive effects become a reality? A new study by the city of Gothenburg aims to answer that.

City authorities and public transport operators worldwide scramble to find out how to best use autonomous vehicles as part of the public transport system, or beside it.

The study in Gothenburg is the first of its kind in Sweden. Like previous studies in Oslo and Lisbon,  it examined the impact of people changing their travel behaviour and switching to autonomous vehicles (AV).

The result is a better understanding of how electric, shared, and self-driving vehicles affect and supplement public transport. It also highlights how the transport system is affected from a sustainability perspective.

Simulating a future of AV

The project team consisted of researchers from the Gothenburg Urban Transport Administration, public transport agency Västtrafik,the Swedish knowledge centre for public transport K2Malmö University, and consultants of Trivector. They modelled possible future scenarios using Gothenburg’s multimodal modelling platform in PTV Visum.

The city generally uses the demand-driven model for infrastructure and mobility planning. For the study, the model was extended by a special MaaS (Mobility as a Service) module to simulate new mobility services.

In this virtual environment, the researchers examined diverse possible developments. Within the simulation, they assumed that the self-driving vehicles travel only in a defined area – the municipalities of Gothenburg, Mölndal and Partille. It is likely that such services will be first introduced in large cities, where they can provide sufficient frequency and be profitable.

The researchers focused on two forms of AV usage:

  • Car-sharing, where people use self-driving services privately, like today’s cars.
  • Ride-sharing, where AVs are shared with other passengers, who have the same destination.

The Scenarios

Self-driving vehicles are perceived today as a comfortable and convenient way of traveling. It’s likely they will become the preferred mode of transport for many. An attractive AV service might especially be an attractive option for users of public transport. If this happens, what will happen to traffic volumes?

The researchers explored 5 scenarios, in which today’s drivers and public transport users switch to autonomous car-sharing – with or without ridesharing. With PTV Visum simulations, they analysed each scenario according to parameters such as travel times, congestion, and CO2 emissions.

The results

The simulation results show that an increase of self-driving vehicles does not automatically result in less traffic – as often predicted. In other words, there may be overall less vehicles in the network, but on average each vehicle drives more hours.

The simulation pointed out, that a switch to autonomous car- and ride-sharing may result in a reduction of up to 80% in the number of overall vehicles.

If today’s drivers will choose the ride-sharing options, traffic volume will decrease by up to 6%. But if they choose the car-sharing option, the traffic will increase by 15%.

If, in addition to drivers, today’s public transport users will switch to AV services, traffic will increase in both the car-sharing and ride-sharing scenarios.

The conclusions

The results of the research demonstrate how important it is for cities to start planning for the impact of switching to autonomous vehicles. Understanding the potential opportunities, risks and consequences that may arise from new technologies, enables them to make solid decisions and thus reliable transport planning..

AVs must be thought of as part of a holistic ecosystem, to ensure they do not increase congestion. The researchers determine that AVs will be most beneficial when integrated into public transport systems as ride-sharing services – and not as today’s private cars. The findings of the study help decision makers to set the right framework conditions to orchestrate the mobility system and shape it in a sustainable way.

Understanding today the future impact of AVs is key to realizing their full potential for people, mobility, and the environment.

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