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CoEXist use cases: What are the first results?

Posted: 05.12.2019
5 December 2019

In the framework of the CoEXist project, microscopic and macroscopic modelling tools were developed to help local authorities to better understand the impacts of automation on their mobility patterns. The four CoEXist cities – Gothenburg (SE), Helmond (NL), Milton Keynes (UK) & Stuttgart (DE) – are the first local authorities to use these tools.

With the support of the research partners, the analysis of the results is made for each of the eight particular CoEXist use cases which focus on different areas such as the capacity of arterial road with signalised junction or mixed road space. While the analysis is still ongoing, some preliminary results are already available, both at the macroscopic and microscopic levels. The preliminary results presented below concern the use cases in Gothenburg and Stuttgart.

Different scenarios have been modeled and analysed to understand the impact of automation on the urban traffic, with different levels of ‘coexistence’ between conventional vehicles (CVs) and automated vehicles (AVs). Indeed, the modelling tools allow to modify the penetration rate of automated vehicles (i.e. share of AVs) and the automation level of AVs (from very cautious behaviours to more ‘fluid’ ones).

Impacts of AVs and the macroscopic…

At the macroscopic level, the results from the use cases in Gothenburg and Stuttgart give similar results. In both cities, in the first phase of the introduction of AVs (limited number of cautious AVs), the automated vehicles perform worse than CVs in terms of speed and therefore they increase travel times for all road users. This also lead to a minor modal shift from cars to other modes. However, as soon as AVs improve traffic performance, traveling by car, either CVs or AVs, becomes more attractive and causes a modal shift towards cars. This is expected to happen when a sufficient number of AVs are introduced (around 30%), including a fair share of advanced AVs. In addition as people are willing to spend more time in their vehicles (with other activities), the total distance traveled increases and could represent an increase of road traffic up to 20%.

In Gothenburg, where several options were tested, it appears that reserving a bottleneck link for AVs only could make the road traffic more fluid during peak hours, and partially solve congestion problems. However, to have a significant impact, AVs should represent at least 30% of the total number of vehicles. On the contrary, allowing AVs to drive on the bus lanes is not recommended as the simulation results show that this does not significantly improve the traffic conditions and even creates delays in the bus schedules.

… and microscopic levels

At the microscopic level, the first results are concerning the mixed-traffic area of Kungstorget, in Gothenburg. In this area, although the impacts are reduced when more AVs and more advanced AVs are present, their introduction means an increase in travel times and more delays. However, it should be noted that the increased travel time is partially caused by a better compliance with speed limits, which is positive for road safety, especially in an area with numerous pedestrians and cyclists.

In addition, the introduction of AVs has nearly no impact on the pedestrians, as their travel time remains stable. However, the speed of automated minibuses is reduced (less than two times faster than pedestrians, in the best cases). The introduction of pedestrian crossings to better define the areas where pedestrians are likely to be present does not improve the speed of minibuses as the flow of pedestrians on the crossing would be almost permanent and would block the passing of vehicles.

As more results will be available, they will be made available on the CoEXist website.