Optimization of MSW Collection Routes in Chengdu Using GIS Network Modeling

The generation of municipal solid waste(MSW) is growing at an annual rate of 8% in China,which causes an increment of cost of MSW collection and transportation.In the integrated management of MSW,MSW collection and transportation is a highly visible and important service,which involves approximately 70% expenditure of the total MSW management.Improper collection and transportation of MSW will cause a tremendous amount of cost,induce a secondary pollution and threaten the life of urban inhabitants.Therefore,it is meaningful to improve waste management efficiency through the design of efficient collection routes for vehicles and scheduling programs for the solid waste collection system.In this paper,the low efficiency and environmental problems of MSW collection system in Shuangnan district of Chengdu are addressed in detail.A project of optimizing MSW collection routes is proposed to reduce collection cost and secondary pollution.A solving model for MSW collection routes is built based on GIS,which presents several characteristics derived from traffic regulations: some streets can be traversed in only one direction;some turns will be forbidden when the common angle is too narrow.And after an appropriate transformation of the problem into a node routing one to reduce the problem scale,a clustering-based ant colony system(CACS) algorithm is presented for obtaining the solutions to the problem.Our CACS approach possesses a set of new strategies to construct solutions,including clustering-based strategy,global pheromone update rule and mutation operation.The results show that the unit collection expense of the optimal routes is 12.3 $/t with turn constraint and 12.2 $/t without it,being a 34.92% and 35.45% reduction compared with pre-optimization cost,respectively.