Paris: east extension of the Tramway des Maréchaux

Client: La Mairie de Paris (Paris city council)

Brief: Evaluate the impact of four designs for the east extension of the T3 tramway, running along the Boulevards des Maréchaux urban ring road in Paris. Provide an optimal revised traffic control plan for each design.

The Marie de Paris commissioned Aimsun to assess the impact of different designs for the new segregated tramway. Urban planners submitted four different scenarios: one axial tramway and three lateral tramways in different configurations.

Assessment of the impact of each design scheme was dependent on their performance under optimised management. Weighing up the potential of management schemes showcases what Aimsun microsimulation does best: considering numerous scenarios, each consisting of a physical design and an associated traffic control strategy with multiple conflicting objectives.

Methodology

To enable the tram to travel without slowing down for signal changes, the existing fixed cycle control plans needed to be complemented by adaptive control (tram pre-emption). This had to square with conflicting priorities such as pedestrian safety or minimising the impact of the tramline on cross streets.

To evaluate the performance of the four designs, Aimsun compared the performance of each design and various associated control plans on the most representative intersection. This enabled Aimsun to fine-tune a traffic control concept for each design.

Quantification of detailed dynamics was essential: vehicles partly blocking an intersection, pedestrians crossing late or trams passing over a detector were all minute details that can make a difference. Aimsun also included stochastic elements and examined a range of possible situations.

The next stage was a global evaluation of the whole test area, from Porte de Vincennes to Porte de Bagnolet, including fifteen signalised intersections and two large signalised roundabouts.

To evaluate safety, Aimsun studied the visual outputs of the simulation and the interactions between trams and other modes; to evaluate capacity, Aimsun collected the numerical outputs (queue lengths at intersections as a function of time), and collated them to summarise the risk of blockage in each scenario.

Conclusions

Simulations of the entire area clearly showed that the axial scenario outperformed the other schemes with respect to the multiple criteria defined by the client.

As an additional benefit, the control plans (including tram pre-emption signal control) that Aimsun designed for this simulation study were then successfully put into practice once the tram was up and running.