TransAID Deliverable 8.2: Meta-analysis of the results

Kurzfassung

The TransAID project defines, develops and evaluates traffic management measures based on V2X equipped road infrastructure, primarily via simulations,to eliminate or mitigate the negative effects of Transition of Control (ToC) along Transition Areas in future mixed traffic scenarios where automated, cooperative, and conventional vehicles will coexist.This document aggregates, integrates, and analyses the results of the TransAID work packages. For each aspect of TransAID the major findings are presented and discussed.As a basis for the simulation studies several vehicle models were implemented successfully to create the right behaviour for lane changing(including cooperative versions), car following (including (C)ACC)and ToC/MRM algorithms. These models were created using a solid theoretical background, however, the availability of real-world data for input and calibration was very limited. From the baseline simulation runs we found that ToCs do not significantly disrupt traffic flow performance unless CAVs establish increased car-following headways during the ToC preparation phase. Disruptions escalate in case of CACC driving, increased share of CAVs in the fleet mix, and the occurrence of multiple ToCs within a narrow temporal window and spatial domain. Furthermore, in the case that a ToC is unsuccessful or not possible, unmanaged MRMs (taking place in lane and not being guided towards safe spots) can induce significant traffic disruption as well. On the other hand, simulation results indicated that cooperative lane changes minimize the frequency of ToC/MRM and their consequent adverse impacts on trafficflow operations. The benefits of cooperative lane changing are amplified with increasing share of CAVs and especially upstream of lanedrop locations.Building upon the vehicle models, simulations and the defined use cases, specific traffic measureswere developed to mitigate the effects of ToC events in transition areas. The traffic measures were implemented to study their effectiveness. Specifically, for each of the selected use cases the effects of the TransAID measures are evaluated regarding emissions, safety and efficiency. There is a trade-off between traffic safety versus traffic efficiency (as measured via throughput and travel times). It is often inherently difficult or even impossible to optimise both in the same context. Hence, typically a policy choice needs to be made, as to which of the two will have to be prioritised. Otherwise, results either improved or remained similar for all use cases and KPIs, with the exception of use case 3.1 (see Section 2.2.2 for details and Table 1at the end of Chapter 6). All use cases have in common that a reduction of MRMs is possible by providing infrastructure advice. Such advice, and the availability of safe spots, clearly reduces the number of stopped vehicles blocking the road.There is also a heavy dependence of the results on the mixture of vehicle types, in addition to the observation that less efficient traffic management performance is obtained for a higher LOS. The latter is in part logical, as for higher LOS there is more prominent congestion and the physical limits of the infrastructure remain a hard obstacle. By itself this is not a problem for TransAID, as the focus of the traffic management schemes is to prevent/postpone traffic breakdowns before they occur. While implementing and testing the traffic measures TransAIDalso identified or created the needed message sets and protocols to implement the measures using V2X communications. To that end, no new message sets wereneeded, but (minor) extensions to CAM, DENM, MCM and MAPEM were necessary. Especially MCM from the Manoeuvre Coordination Service (MCS) is key to multiple types of use case. Therefore, it is necessary to define a MCS that is valid for all types of scenarios. Aligned with the work of ETSI and by actively contributing, TransAID has proposed a MCS where the infrastructure takes an active role to facilitate the manoeuvres of vehicles and to increase the overall traffic flow and safety. The traffic management measures designed in TransAID also require that CAVs and road infrastructure units have an accurate perception of the environment. In addition to the MCS, TransAID has contributed to the evaluation and evolution of ETSI's Collective Perception Service (CPS) for cooperative perception. We have demonstrated that cooperative perception can improve CAVs perception capabilities when the trade-off between the perception capabilities and communications performance is balanced. Furthermore, the reliability of V2X communications has been addressed in TransAID using different and complementary techniques: compression, congestion control and acknowledgements.Besides the V2X communication, the communication to unequipped vehicles was of importanceand consisted of two parts. On the one hand, infrastructure needs to inform unequipped vehicles about issues on the road. On the other, automated vehicles themselves should provide information about their actual state to their surroundings, to avoid negative impacts.With regards to the infrastructure information, it needs to be mentioned that visual information on signs, variable or static, will never be as precise as V2X communication could be, esp. when looking to individual advices. Nevertheless, infrastructure can provide valuable information also to unequipped vehicles by signage, e.g., in terms of speed limits, distance (gap) advice or dynamic lane assignments.It will be required to create additional road signs dealing with automated vehicles, at least showing that, e.g.,an area is prohibited for automated vehicles or an area where only automated vehicles are allowed.Regarding signals from automated vehicles, TransAID's solution of having LED light strips at the back of AVswill be beneficial in any case, but the exact content of such lights needs to be defined by performing more detailed analyses of such components. This goes to all external and dynamic HMI components of automated vehicles. In this light, it will be crucial to have an intuitive way of understanding the automation related additional information. One key question in this area is if driving with enabled automation should be indicated by an additional external light, and if so, where should this light be and whatcolour?Combining the work on the traffic measures and communications, the iTETRIS framework was used to evaluate the selected use cases while deploying the traffic measures using V2X. The goal was to see if the V2X communications impacted the effectiveness of the measures in any way.After adding V2X, the simulation results forthe project's first and second iteration use cases showed very similar results to the previous evaluation. All traffic measures were found robust enough to show the same results as with idealV2X, even in light of increased traffic demand and thus more V2X enabled vehicles.There were some minor differences between the realistic V2X and ideal V2X implementations, but those could be traced back to easily fixed technical aspects (see Section 2.4 for details). As a final step in our use case assessment,the feasibility of measures and communications introduced were implemented in real-world demonstrators. The real-world implementation was done by performing three different feasibility assessments. Two of them have been performed on test tracks in Germany, and one on public roads in The Netherlands. On the test tracks, several detailed tests of all scenarios have been performed, revealing that all traffic management measures could be successfully integratedand applied to automated vehicles in all use cases and scenarios. This includes the successful setup of the RSI and the automated vehicles. It has to be mentioned, though, that the implementation was done in a prototypic way.The development of related series products would require much more testing under real world conditions, which will be challenging at the current time since no highly automated vehicles are present on the roads. Nevertheless, it is very important to start the investigations at present times. As already described in Section 3.3, standardisation of messages is happening already now, and it was very important to include the role of the infrastructure at this stage. The detailed results of the real-world implementations per use case can be found in Section 2.5.In addition to the design and technical implementation of traffic measures in simulation and the real-world, TransAID gained some insights on issues of a less technical nature. For example, it was determined a close collaboration between OEMs and (N)RAs would be beneficial in the identification and managing of TAs. To facilitate such a collaboration TransAID proposes a traffic management frameworkin the form of an intermediary service provider, acting as a trusted (and possibly mandated) third party. The framework allows TransAID to be scaled up and generalised. We approached this from both a technical and a business-oriented perspective. For TransAID to become part of a complete traffic management system, we focused on the technical side on how to detect transition areas, select (and possibly combine) services, and then detect when they are most appropriately timed for deployment. To this end, detection can be done via the infrastructure (e.g. road sensors or even digital communication infrastructure), via the OEMs, or by comparing an infrastructure's newly-defined ISAD level (Infrastructure Support levels for Automated Driving; see Section 1.4.2) to theoperational design domain (ODD, see Section 1.4.1) of the vehicle.Considering the mentioned technical challenges (detecting TAs, selecting services, and timing their deployment), the intermediary service bridges all these parties in such a way that the detection of TAs is performed in a centralised way, and OEMs and (national) road authorities ((N)RAs) have a single point of contact for providing and receiving information about TAs.Another point where OEMs and (national) authorities could collaborate,is the legislation related to automated driving since an important gap in current modelling and legalisation is how (C)AVs would/should react when (given) advice and/or actions conflict with traffic laws. With the real-time coordinated instructions of a TMC, (C)AVs should drive adequately during their journeys. However, it is necessary to concern to what extent such instructions should/can be made, especially when considering legal issues.In addition, legal aspects like the definition of special signage for automated vehicles and their handlingalso need to be considered, as those aspects will take time. This also means signage at the roadside, including VMS content, and signage from automated vehicles to surrounding traffic.Collaboration is also required regarding the definition and standardisation of V2X messages and protocols. The mechanisms proposed in TransAID to improve the reliability of V2X messages can be key in the near future. In general, V2X communications solutions require to be incorporated into standards to be effectively deployed. That is the case for, for example, collective perception solutions, message generation rules for manoeuvre coordination, V2X message compression or broadcast acknowledgement mechanisms. In TransAID we have been intensively working to promote and disseminate all the proposed solutions in top-tier journals and international conferences, as well as in organisations like ETSI and C2C-CC. The above shows a broad range of aspects studied by TransAID in the very dynamic and rapidly evolving field of automated driving.To provide links to additional information and to place the work of TransAID into context, Chapter 5 provides an overview or close related initiatives.