Beyond Prediction: On-street Parking Recommendation using Heterogeneous Graph-based List-wise Ranking
This addresses the problem of inefficient parking search for drivers in urban areas, representing an incremental improvement by shifting from prediction to direct recommendation.
The paper tackles the problem of reducing drivers' cruising time by directly recommending on-street parking spaces, proposing a learn-to-rank model called OPR-LTR that uses a heterogeneous graph (ESGraph) to represent turnover events and geographical relations, achieving satisfactory performance in metrics and improved efficiency compared to prediction-based methods.
To provide real-time parking information, existing studies focus on predicting parking availability, which seems an indirect approach to saving drivers' cruising time. In this paper, we first time propose an on-street parking recommendation (OPR) task to directly recommend a parking space for a driver. To this end, a learn-to-rank (LTR) based OPR model called OPR-LTR is built. Specifically, parking recommendation is closely related to the "turnover events" (state switching between occupied and vacant) of each parking space, and hence we design a highly efficient heterogeneous graph called ESGraph to represent historical and real-time meters' turnover events as well as geographical relations; afterward, a convolution-based event-then-graph network is used to aggregate and update representations of the heterogeneous graph. A ranking model is further utilized to learn a score function that helps recommend a list of ranked parking spots for a specific on-street parking query. The method is verified using the on-street parking meter data in Hong Kong and San Francisco. By comparing with the other two types of methods: prediction-only and prediction-then-recommendation, the proposed direct-recommendation method achieves satisfactory performance in different metrics. Extensive experiments also demonstrate that the proposed ESGraph and the recommendation model are more efficient in terms of computational efficiency as well as saving drivers' on-street parking time.