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Preparation of road infrastructure will help to harmonise and steer traffic flows

Soon road traffic will comprise a mixture of automated and non-automated vehicles. However, studies of real-world and computer-simulated mixed traffic flows show that efficiency and safety could decrease if no measures are taken to support the transition to automated driving and the coexistence of conventional and automated vehicles.

Transport and Mobility

This EU-funded INFRAMIX project investigated solutions for improving mixed traffic situations where automated and non-automated vehicles share the road. “INFRAMIX focused on how vehicles and drivers can be supported by new elements of physical and digital traffic infrastructure,” states project coordinator Martin Dirnwöber. Consortium members designed, upgraded, adapted and tested both physical and digital elements of the road infrastructure to ensure an uninterrupted, predictable, safe and efficient traffic flow. “This included ways of informing all types of vehicles about the road operator’s control commands, proposing new visual signs and electronic signals, whilst making sure the proposed adaptations do not jeopardise safety or quality of service,” Dirnwöber explains.

More information for drivers

Three key traffic scenarios formed the basis of INFRAMIX’s work. The first involved the assignment of lanes dedicated solely to automated traffic, while the second studied roadworks zones as major safety hotspots requiring efficient coordination of mixed traffic flows. The final scenario investigated the use of bottlenecks for real-time control of mixed traffic to avoid traffic flow degradation. Researchers developed algorithms for estimating traffic based on highly accurate real-time data. “These algorithms enabled the number of road sensors and related costs to be reduced by using data from connected vehicles,” notes Dirnwöber. “They also established simulation environments to evaluate different aspects of efficiency and traffic safety control strategies in mixed traffic environments, coupling them with real-world testing to enhance the scope of evaluation.” In addition, INFRAMIX developed an acceleration controller (ACC) to increase efficiency by adjusting the desired time gap to the leading vehicle. A mainstream traffic flow controller was also designed to provide information to drivers via variable speed limits (VSLs) message signs as was a controller for lane change advice for connected vehicles at bottlenecks.

Greater efficiency

These measures were implemented in both the real world and simulation environments, including a combination of virtual and real-world testing. According to Dirnwöber: “The application of an ACC time gap controller could improve efficiency in case of delays by some 50 %. Meanwhile, advice on speed, communicated via VSLs to address conventional vehicles and via electronic messages to address connected and automated vehicles, could decrease delay times by 10 to 15 %.” When applied to a network, the infrastructure classification scheme for automated driving developed by INFRAMIX provides a clear overview of the functionalities of different levels of infrastructure support to automated driving. Furthermore, the traffic control strategies and the required physical and digital infrastructure, including the INFRAMIX management centre, have been implemented in two real-world test sites in Austria and Spain. INFRAMIX provided concrete solutions for improving efficiency and safety in areas containing roadwork zones and bottlenecks, which also could reduce emissions. “The project benefits stakeholder groups, such as policymakers, infrastructure operators, industry, researchers and key influencers in particular. In addition, the general public will benefit from a more efficient transport system once such solutions are implemented,” Dirnwöber points out.

Keywords

INFRAMIX, traffic, infrastructure, automated vehicles, acceleration controller, variable speed limits, transport

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