Variable Speed Limit Optimization With Environmental Concern

This paper proposes a model to optimize the variable speed limit with environmental concerns. The traffic simulation model, emission model and dispersion model are combined into the evaluation model. Based on the traffic information obtained through cell-based flow propagation, the modal emission approach is employed to estimate the driving mode of vehicles in each cell. Then the vehicular emissions for each cell will be calculated based on the driving mode. Subsequently, the Gaussian plume dispersion model is applied to capture the dispersion process of air pollutants and determine the roadside pollutant concentrations. Next, a performance measure based on human emission exposure is built to quantify the negative environmental impact.The optimization model is solved by simulation-based Genetic Algorithm. The structure of the chromosome is discussed first. With an initial pool of solutions, the processes of crossover and mutation are performed to generate, the new generation. Further steps of filter, revision or rejection are needed to make sure the individuals in new generation are practicable. Then the evaluation model will calculate the fitness of each individual, which determined their probability to be selected into next generation.Some numerical tests are performed to demonstrate the proposed model and algorithm.