Road Traffic Congestion Monitoring in Social Media with Hinge-Loss Markov Random Fields

Real-time road traffic congestion monitoring is an important and challenging problem. Most existing monitoring approaches require the deployment of infrastructure sensors or large-scale probe vehicles. Their installation is often expensive and temporal-spatial coverage is limited. Probe vehicle data are oftentimes noisy on urban arterials, and therefore insufficient to provide accurate congestion estimation. This paper presents a novel social-media based approach to traffic congestion monitoring, in which pedestrians, drivers, and passengers a retreated as human sensors and their posted tweets in Twitter as observations of nearby ongoing traffic conditions. There are three technical challenges for road traffic monitoring based on Twitter, namely: 1) language ambiguity in the usage of traffic related terms, 2) uncertainty and low resolution of geographic location mentions, and 3) interactions between traffic-related events such as accidents and congestion. We propose a topic modeling based language model to address the first challenge and a collaborative inference model based on probabilistic soft logic (PSL) to address the second and third challenges. We present a unified statistical framework that combines those two models based on hinge loss Markov random fields (HLMRFs). In order to address the computational challenges incurred by the non-analytical integral of latent variables (factors) and the MAP estimation of a large number of location-dependent traffic congestion variables, we propose a fast approximate inference algorithm based on maximization expectation (ME) and the alternating directed method of multipliers (ADMM). Extensive evaluations over a variety of metrics on real world Twitter and INRIX probe speed datasets in two U.S. Major cities demonstrate the efficiency and effectiveness of our proposed approach.