Dear Mirko,
Thank you for your prompt and insightful response. In the past, like many others, I assumed that congestion naturally occurs when vehicles are added on a road section, but the reality is more complicated. However, I was hoping to find an alternative approach to replicate the phenomenon without introducing a bottleneck. In the past, Jakob suggested using a closed loop to replicate the phenomenon. Is this the sole method to achieve it? But I understand that it may not be possible otherwise. The preference for a straight road is to enhance conference presentation clarity, as a bottleneck or loop could be challenging for the audience. I appreciate your assistance and welcome any further insights. Kind regards, François Québec city , CANADA ________________________________ De : Mirko Barthauer <[email protected]> Envoyé : lundi 15 janvier 2024 06:26 À : Sumo project User discussions <[email protected]> Cc : François Vaudrin <[email protected]> Objet : AW: [sumo-user] Validation of BPR Method in SUMO: Seeking Help on Replicating Asymptotic Results in Straight Road Sections Dear François, as you already noted, travel times on inflow edges depend a lot on the insertion rules and the used car-following settings. The next vehicle to be inserted needs some space (vehicle length and distance to leader) and only one vehicle per time step and lane can enter the network. To some extent, your question is similar to "how to replicate the fundamental diagram in sumo" (especially the saturated part). You need some way to increase the vehicle density which will lead to longer travel times. Either create an artificial bottleneck or let vehicles circulate in the network for longer and keep some distance from inflow places when measuring the travel time. Best regards Mirko -----Original-Nachricht----- Betreff: [sumo-user] Validation of BPR Method in SUMO: Seeking Help on Replicating Asymptotic Results in Straight Road Sections Datum: 2024-01-15T08:29:15+0100 Von: "François Vaudrin via sumo-user" <[email protected]> An: "Sumo project User discussions" <[email protected]> Hello, I'm seeking assistance in validating the BPR method using SUMO to express travel time based on road capacity. The Bureau of Public Roads (BPR) formula is commonly used to model travel time on a road as a function of its capacity: After reaching a certain flow threshold, travel time increases exponentially until reaching the ultimate capacity of the road. [X] where: * T is the travel time on the road, * Tff is the initial travel time, * q is the flow of traffic (number of vehicles per unit time), * qpc is the capacity of the road (maximum number of vehicles the road can accommodate per unit time), * α and β are adjustable parameters. Despite increasing the flow of vehicles in a network with SUMO, Vehicles are being pushed backward before entering the network, possibly due to a required distance (likely related to the car-following model), but the results are not the same than BPR. The Time Tff appears to be a straight line rather than an asymptotic curve. Appreciating any insights or suggestions to obtain similar results of BPR? Wishing a fantastic year ahead to the SUMO teams and contributors! François Vaudrin semaphor.ai Québec city, Canada
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