Arc Routing for Parking Enforcement Officers: Exact and heuristic solutions

Abstract

This paper presents exact and approximate methods for constructing daily walking tours for parking enforcement officers the Parking Enforcement Routing Problem (PERP), a problem faced by EMEL, a municipal company that manages parking in Lisbon. Parking Enforcement Officers (PEO) must ensure that the users of the street parking lots pay the corresponding fee, and that they also comply with the parking rules imposed by the legislation in force. The duration of the tours must be compatible with the PEO daily work schedules. A street cannot be supervised more than once in consecutive hours, nor supervised simultaneously by two PEOs. The PERP is a new generalisation of an Arc Routing Problem with profits aiming to maximise the total criticality, a concept defined to represent the need for enforcement of the street segments, related to the number of vehicles parked in transgression. Moreover, parking rules lead to some specificities regarding the underlying network, which needs to be built with additional unusual characteristics. A flow-based mixed integer linear programming model and heuristics which return two daily trips for each PEO are proposed. Computational results carried out on 50 instances based on real data show that it was appropriate to propose both types of methods, exact and heuristic. Furthermore, PEOs working for EMEL reacted positively to the trips corresponding to the generated solutions. A Decision Support System built on the heuristics was also developed to be easily used by practitioners in EMEL.