Full Bayesian Before-After Analysis of Safety Effects of Variable Speed Limit System

Variable speed limits (VSL) is a major Intelligent Transportation System (ITS) technology for controlling freeway mainline traffic, which have been increasingly used to improve traffic safety and operations efficiency of freeway traffic management. The primary objective of this study is to evaluate the safety impacts of the VSL system implemented on Interstate 5 in Seattle, United States since 2010. A Full Bayesian (FB) before-after analysis was conducted based on 9,787 crashes that occurred in a 72-month study period. The analysis was conducted for all crashes, crash severity levels, crash types, and crash causes. The FB before-after results implied that the total crash count was reduced by 32.23% with a standard deviation of 3.58% after the VSL system was applied on the freeway. The count of crashes with no injury decreased more than crashes with severe injury and possible injury. The effect of rear-end crash reduction was the most beneficial among all crash types, while the effect on sideswipe crash reduction was the least. The study also compared the traffic speed features in the before and after periods to fully evaluate the impacts of the VSL system on traffic operations. The result indicated that, with VSL control, the difference in speed was reduced by the VSL system. The results of this study are particularly valuable for policy and control strategy development, and cost-benefit evaluation associated with VSL system implementations.

[1]  C. Hydén,et al.  Evaluation of traffic safety, based on micro-level behavioural data: theoretical framework and first implementation. , 2010, Accident; analysis and prevention.

[2]  Feng Guo,et al.  Driver crash risk factors and prevalence evaluation using naturalistic driving data , 2016, Proceedings of the National Academy of Sciences.

[3]  M. Papageorgiou,et al.  Effects of Variable Speed Limits on Motorway Traffic Flow , 2008 .

[4]  Mohamed M. Ahmed,et al.  Investigating the Impact of Fog on Freeway Speed Selection using the SHRP2 Naturalistic Driving Study Data , 2018, Transportation Research Record: Journal of the Transportation Research Board.

[5]  Bhagwant Persaud,et al.  Fully Bayesian Approach to Investigate and Evaluate Ranking Criteria for Black Spot Identification , 2011 .

[6]  Bryan J Katz,et al.  Synthesis of Variable Speed Limit Signs , 2017 .

[7]  Hojjat Adeli,et al.  TOWARD INTELLIGENT VARIABLE MESSAGE SIGNS IN FREEWAY WORK ZONES: NEURAL NETWORK MODEL , 2004 .

[8]  Mehdi Hosseinpour,et al.  Exploring the effects of roadway characteristics on the frequency and severity of head-on crashes: case studies from Malaysian federal roads. , 2014, Accident; analysis and prevention.

[9]  Jonathan Aguero-Valverde,et al.  Full Bayes Poisson gamma, Poisson lognormal, and zero inflated random effects models: Comparing the precision of crash frequency estimates. , 2013, Accident; analysis and prevention.

[10]  Bhagwant Persaud,et al.  COMMON BIAS IN BEFORE-AND-AFTER ACCIDENT COMPARISONS AND ITS ELIMINATION , 1983 .

[11]  S. E. Ahmed,et al.  Markov Chain Monte Carlo: Stochastic Simulation for Bayesian Inference , 2008, Technometrics.

[12]  Zhiyong Cui,et al.  Digital roadway interactive visualization and evaluation network applications to WSDOT operational data usage. , 2016 .

[13]  Dot Hs,et al.  The 100-Car Naturalistic Driving Study Phase II - Results of the 100-Car Field Experiment , 2006 .

[14]  Paul P Jovanis,et al.  Using naturalistic driving data to explore the association between traffic safety-related events and crash risk at driver level. , 2014, Accident; analysis and prevention.

[15]  Mohamed Abdel-Aty,et al.  Modeling rear-end collisions including the role of driver's visibility and light truck vehicles using a nested logit structure. , 2004, Accident; analysis and prevention.

[16]  Feng Guo,et al.  Individual driver risk assessment using naturalistic driving data. , 2013, Accident; analysis and prevention.

[17]  Bhagwant Persaud,et al.  Validation of a Full Bayes methodology for observational before-after road safety studies and application to evaluation of rural signal conversions. , 2009, Accident; analysis and prevention.

[18]  Ziyuan Pu,et al.  Evaluating Safety Effects of Variable Speed Limit System using Empirical Bayesian Before-After Analysis , 2017 .

[19]  Mohamed Abdel-Aty,et al.  Evaluation of variable speed limits for real-time freeway safety improvement. , 2006, Accident; analysis and prevention.

[20]  Michael Pawlovich,et al.  FROM EMPIRICAL BAYES TO FULL BAYES: METHODS FOR ANALYZING TRAFFIC SAFETY DATA , 2004 .

[21]  Pedro M. Valero-Mora,et al.  Geo-referencing naturalistic driving data using a novel method based on vehicle speed , 2013 .

[22]  Asad J. Khattak,et al.  Injury Severity in Multivehicle Rear-End Crashes , 2001 .

[23]  Pedro M. Valero-Mora,et al.  Proposal of Geographic Information Systems Methodology for Quality Control Procedures of Data Obtained in Naturalistic Driving Studies , 2015 .

[24]  Bhagwant Persaud,et al.  Safety Effect of Roundabout Conversions in the United States: Empirical Bayes Observational Before-After Study , 2001 .

[25]  Bruce Hellinga,et al.  Variable Speed Limits: Safety and Operational Impacts of a Candidate Control Strategy for Freeway Applications , 2007, IEEE Transactions on Intelligent Transportation Systems.

[26]  Chris Lee,et al.  Evaluation of Variable Speed Limits to Improve Traffic Safety , 2006 .

[27]  Ahmed E. Radwan,et al.  Modeling traffic accident occurrence and involvement. , 2000, Accident; analysis and prevention.

[28]  Ali Darroudi.  Variable Speed Limit Strategies to Reduce the Impacts of Traffic Flow Breakdown at Recurrent Freeway Bottlenecks , 2014 .

[29]  Yinhai Wang,et al.  Quantifying Incident-Induced Travel Delays on Freeways Using Traffic Sensor Data: Phase II , 2008 .

[30]  Md. Mazharul Haque,et al.  Empirical Evaluation of Alternative Approaches in Identifying Crash Hot Spots , 2009 .

[31]  Fedel Frank Saccomanno,et al.  Assessing Safety Benefits of Variable Speed Limits , 2004 .

[32]  Berné,et al.  REPRESENTATION OF KINEMATIC DRIVING BEHAVIOUR USING GEOGRAPHIC INFORMATION SYSTEMS ( GIS ) , .

[33]  Pedro F. Miret,et al.  Wikipedia , 2008, Monatsschrift für Deutsches Recht.

[34]  Mark P. Haselkorn,et al.  IMPROVED ESTIMATES OF TRAVEL TIME FROM REAL TIME INDUCTANCE LOOP SENSORS. FINAL TECHNICAL REPORT , 1993 .

[35]  Melisa D Finley,et al.  Guidelines for the Use of Variable Speed Limit Systems in Wet Weather , 2012 .

[36]  Ezra Hauer,et al.  OBSERVATIONAL BEFORE-AFTER STUDIES IN ROAD SAFETY -- ESTIMATING THE EFFECT OF HIGHWAY AND TRAFFIC ENGINEERING MEASURES ON ROAD SAFETY , 1997 .

[37]  Bruce Hellinga,et al.  Impact of Driver Compliance on the Safety and Operational Impacts of Freeway Variable Speed Limit Systems , 2011 .

[38]  M. Abdel-Aty,et al.  Potential Real-Time Indicators of Sideswipe Crashes on Freeways , 2006 .

[39]  Kenneth L Campbell.  The SHRP 2 Naturalistic Driving Study: Addressing Driver Performance and Behavior in Traffic Safety , 2012 .

[40]  P Pisano,et al.  BEST PRACTICES FOR ROAD WEATHER MANAGEMENT, VERSION 2.0 , 2003 .

[41]  Bhagwant Persaud,et al.  Comparison of empirical Bayes and full Bayes approaches for before-after road safety evaluations. , 2010, Accident; analysis and prevention.

[42]  H Mackie,et al.  New Zealand's rural intersection active warning system , 2014 .

[43]  Juha Luoma,et al.  EFFECTS OF VARIABLE SPEED LIMIT SIGNS ON SPEED BEHAVIOUR AND RECALL OF SIGNS , 1998 .

[44]  Dot Hs,et al.  The Impact of Hand-Held And Hands-Free Cell Phone Use on Driving Performance and Safety-Critical Event Risk , 2013 .

[45]  P. Rämä.  Effects of Weather-Controlled Variable Speed Limits and Warning Signs on Driver Behavior , 1999 .

[46]  Peter Green,et al.  Markov chain Monte Carlo in Practice , 1996 .

[47]  Bhagwant Persaud,et al.  Empirical Bayes before-after safety studies: lessons learned from two decades of experience and future directions. , 2007, Accident; analysis and prevention.

[48]  P S Parsonson,et al.  TRAFFIC DETECTOR HANDBOOK , 1985 .

[49]  Bart De Schutter,et al.  Model predictive control for optimal coordination of ramp metering and variable speed limits , 2005 .

[50]  Mark Robinson.  Examples of variable speed limit applications : speed management workshop , 2000 .