A novel methodology for determining low-cost fine particulate matter street sweeping routes

This paper addresses the problem of low-cost PM₁₀ (particulate matter with aerodynamic diameter <10 μm) street sweeping route. In order to do so, only a subset of the streets of the urban area to be swept is selected for sweeping, based on their PM₁₀ emission factor values. Subsequently, a low-cost route that visits each street in the set is computed. Unlike related problems of waste collection where streets must be visited once (Chinese or Rural Postman Problem, respectively), in this case, the sweeping vehicle route must visit each selected street exactly as many times as its number of street sides, since the vehicle can sweep only one street side at a time. Additionally, the route must comply with traffic flow and turn constraints. A novel transformation of the original arc routing problem into a node routing problem is proposed in this paper. This is accomplished by building a graph that represents the area to sweep in such a way that the problem can be solved by applying any known solution to the Traveling Salesman Problem (TSP). As a way of illustration, the proposed method was applied to the northeast area of the Municipality of Santiago (Chile). Results show that the proposed methodology achieved up to 37% savings in kilometers traveled by the sweeping vehicle when compared to the solution obtained by solving the TSP problem with Geographic Information Systems (GIS) - aware tools. Implications: The exposure to PM₁₀ has been shown to be harmful to human health. Street sweeping is an effective mitigating measure used to reduce the amount of PM₁₀. This paper proposes a generic method to determine a low-cost PM₁₀ sweeping route. This problem has seldom been studied in the literature, with only two previous papers focusing on solving it under very specific circumstances, which makes them not applicable to generic scenarios. By providing a generic method that solves the problem under different scenarios, it is expected to facilitate the decision-making process of environmental and other public agencies regarding the implementation of sweeping routes.