Smart Traffic Load Balancing for Sustainable Cities
By simulation is the effect of this routing system shown on the NOx concentrations and traffic distributions. An estimation of the NOx concentrations in the area is made by combining emission traces of the routes of all vehicles in the area. Different scenarios have been configured and compared to a base case, in which every vehicle minimizes its travel time. The `BalanCity - NOx and CO2' configuration assigns the same importance to the travel time, global CO2 emission and the local air quality. The `BalanCity - CO2 only' configuration minimizes the global CO2 emission, with an upperbound on the individual travel time.
The scientific research and a description of the assumptions can be found in the Master's thesis of P.L. de Goffau.
The following table shows the numerical results of a simulation on the area of Amsterdam from 16:40 to 18:09. The Total Route Time represents the sum of the travel times of all routes, with no congestion. Based on these routes an estimation of the traffic distribution can be made. An estimation of the total time that all vehicles spent together in traffic jams can be made by using the traffic densities. Using a triangular fundamental diagram, an estimation can be made of the reduced speed at congested edges. This speed reduction is multiplied by the number of vehicles at those edges at every timeframe, which results in an estimation of the total travel time loss (in the table represented by 'Congestion Time'. The total travel time is a combination of the total route time and the total congestion time. Based on the routes of vehicles, an estimation can be made of the total emission of CO2 (Total CO2 emission), and the NOx concentrations. If the NOx concentrations exceed a certain bound (threshold), the air quality is regarded as unhealthy. The total exceedance of the NOx threshold (200 [µg/m3]) at all measurement points and all timeframes is represented by the row 'Total exceedance of NOx threshold'.
From the results we can derive that the air quality can be improved by choosing different routes. Without congestion these routes would result in a slightly larger travel time, but if we take congestion into account, the travel time might even be reduced. This is caused by traffic dispersion, as a result of the avoidance of high NOx concentrations.
|Base case||BalanCity - NOx and CO2||BalanCity - CO2 only|
|Total Route Time [h]||40901||42086 (+2.9%)||42812 (+4.7%)|
|Congestion time [h]||5353||3831||3680|
|Total travel time [h]||46254||45917 (-0.7%)||46492 (+0.5%)|
|Total CO2 emission [Mg]||504.6||495.6 (-1.8%)||477.5 (-5.4%)|
|Total exceedance of NOx threshold [g/m3]||1.199||0.5239 (-56.3%)||0.5642 (-52.9%)|