title: Applying quantile regression for modeling equivalent property damage only crashes to identify accident blackspots.
abstract: Hot spot identification (HSID) aims to identify potential sites-roadway segments, intersections, crosswalks, interchanges, ramps, etc.-with disproportionately high crash risk relative to similar sites. An inefficient HSID methodology might result in either identifying a safe site as high risk (false positive) or a high risk site as safe (false negative), and consequently lead to the misuse the available public funds, to poor investment decisions, and to inefficient risk management practice. Current HSID methods suffer from issues like underreporting of minor injury and property damage only (PDO) crashes, challenges of accounting for crash severity into the methodology, and selection of a proper safety performance function to model crash data that is often heavily skewed by a preponderance of zeros. Addressing these challenges, this paper proposes a combination of a PDO equivalency calculation and quantile regression technique to identify hot spots in a transportation network. In particular, issues related to underreporting and crash severity are tackled by incorporating equivalent PDO crashes, whilst the concerns related to the non-count nature of equivalent PDO crashes and the skewness of crash data are addressed by the non-parametric quantile regression technique. The proposed method identifies covariate effects on various quantiles of a population, rather than the population mean like most methods in practice, which more closely corresponds with how black spots are identified in practice. The proposed methodology is illustrated using rural road segment data from Korea and compared against the traditional EB method with negative binomial regression. Application of a quantile regression model on equivalent PDO crashes enables identification of a set of high-risk sites that reflect the true safety costs to the society, simultaneously reduces the influence of under-reported PDO and minor injury crashes, and overcomes the limitation of traditional NB model in dealing with preponderance of zeros problem or right skewed dataset.
authors: Civil Engineering and Built Environment, Science and Engineering Faculty and Centre for Accident Research and Road Safety (CARRS-Q), Faculty of Health, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, QLD 4001, Australia. Electronic address: simon.washington@qut.edu.au.
authors: Simon
authors: S
authors: Washington
authors: Centre for Accident Research and Road Safety (CARRS-Q), Faculty of Health and Civil Engineering and Built Environment, Science and Engineering Faculty, Queensland University of Technology, 130 Victoria Park Road, Kelvin Grove, QLD 4059, Australia. Electronic address: m1.haque@qut.edu.au.
authors: Md Mazharul
authors: MM
authors: Haque
authors: The Korea Transport Institute, 2311 Daehwa-dong, IIsanseo-gu, Goyang-si, Gyeonggi-do 411-701, Republic of Korea. Electronic address: jutaek@koti.re.kr.
authors: Jutaek
authors: J
authors: Oh
authors: The Korea Transport Institute, 2311 Daehwa-dong, IIsanseo-gu, Goyang-si, Gyeonggi-do 411-701, Republic of Korea. Electronic address: dmlee@koti.re.kr.
authors: Dongmin
authors: D
authors: Lee
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D001499:Bayes Theorem; D004779:Environment Design / Q000706:statistics & numerical data*; D006801:Humans; D015233:Models, Statistical; D012044:Regression Analysis
keywords: Empirical Bayes’; Hot spots; Negative binomial regression; Network screening; Non-parametric models; Quantile regression