How is traffic safety affected by changes in traffic speeds following speed limit increases? An evaluation with probe vehicle data
DOI:
https://doi.org/10.55329/xsjw3584Keywords:
75 mph, crash frequency modelling, rural freeway, speed limit increase, speed varianceAbstract
Maximum speed limits continue to be an important policy issue. Research has consistently shown speeds to increase following speed limit increases. These increases have also generally coincided with increases in both the frequency and severity of crashes. However, research has been more limited as to the direct relationship between speed and safety. To this end, the present study evaluates the effects of increasing speed limits on the safety of rural limited access freeways while accounting for contemporaneous changes in the speed profiles of these same roadways. The speed limit increases in Michigan occurred between May 1 and June 12 of 2017, when the maximum speed limits were increased from 70 to 75 mph on approximately 600 miles of freeways. The maximum speed limits for trucks were also increased from 60 to 65 mph on all freeways state-wide at this same time. Speed data were obtained for the Michigan rural freeway network through probe vehicles. These data are merged with pertinent roadway data, as well as police-reported crash data at various levels of injury severity. The impacts of the speed limit increase on safety were evaluated by estimating random effects negative binomial models as part of a case-control before-after study design. The results show that the locations where the speed limits were increased experienced a 5% increase in crashes, while a marginal reduction in crashes was observed where speed limits did not increase. Interestingly, mean speeds were found to be negatively associated with crash frequency, while the standard deviation of speed was found to exhibit a positive relationship. Several site-specific characteristics were also found to be strong predictors of crash frequency. The results provide important insights into the nature of the relationship between speed and safety and will help to guide subsequent speed limit policy decisions.
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Author Biographies
Nischal Gupta, Michigan State University, USA
Nischal Gupta is a third year PhD student and graduate research assistant in the Department of Civil and Environmental Engineering. His research interests mainly focus on traffic safety and operations. He is currently working on multiple research projects including investigating the operational and safety benefits of changes in speed limits, effect of COVID-19 on traffic patterns, and supporting Ford Motor Company in the continued development and refinement of Ford’s Safety Insights.
CRediT statement: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Writing—original draft.
Megat Usamah Megat Johari, Michigan State University, USA
Megat Usamah Megat Johari is a research associate at Michigan State University in the Department of Civil and Environmental Engineering. His research interest includes transportation safety, highway design, traffic operations, and driver behavior. He is involved in various projects including, updating the policy on geometric design of highways and streets; evaluating the effectiveness of safety messages on dynamic message sign; assessing the impact of speed limit increase on traffic safety and operations; and developing a comprehensive access management policy and guidelines.
CRediT statement: Formal analysis, Methodology, Visualization, Writing—original draft.
Hisham Jashami, Oregon State University, USA
Dr. Hisham Jashami is an Assistant Professor (Sr Res) of Transportation Engineering in the School of Civil and Construction Engineering at Oregon State University (OSU) and a certified Road Safety Professional Engineer. Prior to his appointment at OSU, Hisham worked as a Research Associate in the Department of Civil and Environmental Engineering at Michigan State University (MSU). His research has been focused on topics related to transportation safety, human factors, driving & bicycling simulators, autonomous vehicle simulation, and data analysis. During the course of his academic career, Dr. Jashami has worked on externally funded research from agencies including the National Highway Traffic Safety Administration, the Federal Highway Administration, the Pacific Northwest Transportation Consortium (PacTrans), and various State Departments of Transportation which has led to the publication of more than 35 peer-reviewed journal articles, conference papers, and technical reports.
CRediT statement: Formal analysis, Validation, Visualization, Writing—review & editing.
Peter T. Savolainen, Michigan State University, USA
Dr. Peter Savolainen is an MSU Foundation Professor and Associate Chair for Graduate Studies in the Department of Civil and Environmental Engineering. His research expertise covers a diverse range of projects in traffic safety, human factors, and statistical and econometric methods of data analysis. His recent work is highlighted by a series of studies leveraging naturalistic driving data to better understand driver behavior precipitating crash and near-crash events. Dr. Savolainen is a registered professional engineer in the state of Michigan.
CRediT statement: Conceptualization, Funding acquisition, Methodology, Project administration, Supervision, Validation, Writing—review & editing.
References
AASHTO (2018), A Policy on Geometric Design of Highways and Streets (Washington D.C., USA: American Association of State Highway and Transportation Officials) 7th edition.
Anastasopoulos, P. C., F. L. Mannering (2016), ‘The effect of speed limits on drivers' choice of speed: A random parameters seemingly unrelated equations approach’, Analytic Methods in Accident Research, 10, 1–11, https://doi.org/10.1016/j.amar.2016.03.001.
Baruya, A. (1998), ‘Speed-accident relationships on European roads’, presented at 9th International Conference on Road Safety in Europe (Bergisch Gladbach, Germany: 21–23 September 1998), http://virtual.vtt.fi/virtual/proj6/master/pre11.pdf, accessed 22 October 2022.
Baum, H. M., A. K. Lund, J. K. Wells (1989), ‘The mortality consequences of raising the speed limit to 65 mph on rural interstates’, American Journal of Public Health, 79 (10), 1392–1395, https://doi.org/10.2105/ajph.79.10.1392.
Binkowski, S. E., T. L. Maleck, W. C. Taylor, T. S. Czewski (1998), ‘Evaluation of Michigan 70-mph Speed Limit’, Transportation Research Record: Journal of the Transportation Research Board, 1640 (1), 37–46, https://doi.org/10.3141/1640-06.
Brown, D. B., S. Maghsoodloo, M. E. McArdle (1990), ‘The safety impact of the 65 mph speed limit: A case study using Alabama accident records’, Journal of Safety Research, 21 (4), 125–139, https://doi.org/10.1016/0022-4375(90)90020-c.
Castillo-Manzano, J. I., M. Castro-Nuño, L. López-Valpuesta, F. V. Vassallo (2019), ‘The complex relationship between increases to speed limits and traffic fatalities: Evidence from a meta-analysis’, Safety Science, 111, 287–297, https://doi.org/10.1016/j.ssci.2018.08.030.
Davis, A., E. Hacker, P. T. Savolainen, T. J. Gates (2015), ‘Longitudinal Analysis of Rural Interstate Fatalities in Relation to Speed Limit Policies’, Transportation Research Record: Journal of the Transportation Research Board, 2514 (1), 21–31, https://doi.org/10.3141/2514-03.
Dissanayake, S., R. Shirazenijad (2018), ‘Safety Evaluation of Raised Speed Limits on Kansas Freeways’ (Manhattan, KS: Kansas State University, Transportation Center), K-TRAN: KSU-16-3, https://rosap.ntl.bts.gov/view/dot/63593, accessed 22 October 2022.
Donnell, E. T., B. Hamadeh, L. Li, J. Wood (2016), ‘70 mph Study’ (Harrisburg, PA: Pennsylvania Department of Transportation), No. FHWA-PA-2016-009-PSU WO 13, https://www.thenewspaper.com/rlc/docs/2016/pa-raiselimit.pdf, accessed 22 October 2022.
Elvik, R. (2005), ‘Speed and Road Safety’, Transportation Research Record: Journal of the Transportation Research Board, 1908 (1), 59–69, https://doi.org/10.1177/0361198105190800108.
Elvik, R. (2013), ‘A re-parameterisation of the Power Model of the relationship between the speed of traffic and the number of accidents and accident victims’, Accident Analysis & Prevention, 50, 854–860, https://doi.org/10.1016/j.aap.2012.07.012.
Elvik, R., A. Vadeby, T. Hels, I. van Schagen (2019), ‘Updated estimates of the relationship between speed and road safety at the aggregate and individual levels’, Accident Analysis & Prevention, 123, 114–122, https://doi.org/10.1016/j.aap.2018.11.014.
Farmer, C. M., R. A. Retting, A. K. Lund (1999), ‘Changes in motor vehicle occupant fatalities after repeal of the national maximum speed limit’, Accident Analysis & Prevention, 31 (5), 537–543, https://doi.org/10.1016/s0001-4575(99)00010-x.
Forbes, G., T. Gardner, H. W. S. McGee, R. (2012), ‘Methods and Practices for Setting Speed Limits: An Informational Report’ (Washington, D.C., USA: Federal Highway Administration), FHWA-SA-12-004, http://safety.fhwa.dot.gov/speedmgt/ref_mats/fhwasa12004/fhwasa12004.pdf, accessed 22 October 2022.
Freedman, M., J. R. Esterlitz (1990), ‘Effect of the 65-mph speed limit on speeds in three states’, Transportation Research Record: Journal of the Transportation Research Board, 1281, 52–61, https://trid.trb.org/view/352136, accessed 22 October 2022.
Friedman, L. S., D. Hedeker, E. D. Richter (2009), ‘Long-term effects of repealing the national maximum speed limit in the United States’, American journal of public health, 99 (9), 1626–1631, https://doi.org/10.2105/AJPH.2008.153726.
Garber, N. J., R. Gadiraju (1992), ‘Impact of Differential Speed Limits on the Speed of Traffic and the Rate of Accidents ’, Transportation Research Record: Journal of the Transportation Research Board, 1375, 44–52, https://trid.trb.org/view/371648, accessed 22 October 2022.
Garber, S., J. D. Graham (1990), ‘The effects of the new 65 mile-per-hour speed limit on rural highway fatalities: A state-by-state analysis’, Accident Analysis & Prevention, 22 (2), 137–149, https://doi.org/10.1016/0001-4575(90)90065-s.
Gargoum, S. A., K. El-Basyouny (2016), ‘Exploring the association between speed and safety: A path analysis approach’, Accident Analysis & Prevention, 93, 32–40, https://doi.org/10.1016/j.aap.2016.04.029.
Gayah, V. V., E. T. Donnell, Z. Yu, L. Li (2018), ‘Safety and operational impacts of setting speed limits below engineering recommendations’, Accident Analysis & Prevention, 121, 43–52, https://doi.org/10.1016/j.aap.2018.08.029.
Godwin, S. R., C. Lave (1992), ‘Effect of the 65 m.p.h. speed limit on highway safety in the U.S.A. (with comments and reply to comments)’, Transport Reviews, 12 (1), 1–14, https://doi.org/10.1080/01441649208716800.
Grabowski, D. C., M. A. Morrisey (2007), ‘Systemwide implications of the repeal of the national maximum speed limit’, Accident Analysis & Prevention, 39 (1), 180–189, https://doi.org/10.1016/j.aap.2006.06.017.
Houston, D. J. (1999), ‘Implications of the 65-MPH Speed Limit for Traffic Safety’, Evaluation Review, 23 (3), 304–315, https://doi.org/10.1177/0193841x9902300303.
Hu, W. (2017), ‘Raising the speed limit from 75 to 80 mph on Utah rural interstates: Effects on vehicle speeds and speed variance’, Journal of Safety Research, 61, 83–92, https://doi.org/10.1016/j.jsr.2017.02.006.
Imprialou, M.-I. M., M. Quddus, D. E. Pitfield, D. Lord (2016), ‘Re-visiting crash–speed relationships: A new perspective in crash modelling’, Accident Analysis & Prevention, 86, 173–185, https://doi.org/10.1016/j.aap.2015.10.001.
Kockelman, K. (2006), ‘Safety Impacts and Other Implications of Raised Speed Limits on High-Speed Roads’ (Washington, D.C., USA: Transportation Research Board), https://doi.org/10.17226/22048.
Kweon, Y.-J., K. M. Kockelman (2005), ‘Safety Effects of Speed Limit Changes’, Transportation Research Record: Journal of the Transportation Research Board, 1908 (1), 148–158, https://doi.org/10.1177/0361198105190800118.
Lave, C. A. (1985), ‘Speeding, Coordination, and the 55 MPH Limit’, The American Economic Review, 75 (5), 1159–1164, https://www.jstor.org/stable/1818655, accessed 22 October 2022.
Ledolter, J., K. S. Chan (1996), ‘Evaluating the Impact of the 65 mph Maximum Speed Limit on Iowa Rural Interstates’, The American Statistician, 50 (1), 79–85, https://doi.org/10.1080/00031305.1996.10473546.
Lynn, C. W., J. D. Jernigan (1992), ‘The Impact of the 65 MPH Speed Limit on Virginia’s Rural Interstate Highways through 1990’ (Virginia, USA: Virginia Transportation Research Council), VTRC 92-R12, https://rosap.ntl.bts.gov/view/dot/19302, accessed 22 October 2022.
Mace, D. J., R. Heckard (1991), ‘Effect of the 65 mph Speed Limit on Travel Speeds and Related Crashes. ’ (Washington, D.C., USA: National Highway Traffic Safety Administration), LRI 91-01, HS-807 764, https://trid.trb.org/view/363052, accessed 22 October 2022.
Martens, M. H., S. Compte, N. A. Kaptein (1997), ‘The Effects of Road Design on Speed Behaviour: A Literature Review’, http://virtual.vtt.fi/virtual/proj6/master/rep231.pdf, accessed 22 October 2022.
McKnight, A. J., T. M. Klein (1990), ‘Relationship of 65-MPH Limit to Speeds and Fatal Accidents’, Transportation Research Record: Journal of the Transportation Research Board, 1281 71–77, http://onlinepubs.trb.org/Onlinepubs/trr/1990/1281/1281-008.pdf, accessed 22 October 2022.
Musicant, O., H. Bar-Gera, E. Schechtman (2016), ‘Impact of Speed Limit Change on Driving Speed and Road Safety on Interurban Roads: Meta-Analysis’, Transportation Research Record: Journal of the Transportation Research Board, 2601 (1), 42–49, https://doi.org/10.3141/2601-06.
National Highway Traffic Safety Administration (1989), ‘The Effects of the 65 mph Speed Limit during 1987: A Report to Congress’ (Washington, D.C., USA: Department of Transportation), DOT HS 807 369, https://doi.org/10.21949/1525301.
Nilsson, G. (2004), ‘Traffic Safety Dimensions and the Power Model to Describe the Effect of Speed on Safety’, PhD thesis, Lund University, Department of Technology and Society, Traffic Engineering, https://lucris.lub.lu.se/ws/portalfiles/portal/4394446/1693353.pdf, accessed 22 October 2022.
Ossiander, E. M., P. Cummings (2002), ‘Freeway speed limits and traffic fatalities in Washington State’, Accident Analysis & Prevention, 34 (1), 13–18, https://doi.org/10.1016/s0001-4575(00)00098-1.
Patterson, T. L., W. J. Frith, L. J. Povey, M. D. Keall (2002), ‘The Effect of Increasing Rural Interstate Speed Limits in the United States’, Traffic Injury Prevention, 3 (4), 316–320, https://doi.org/10.1080/15389580214625.
Pezoldt, V. J., R. Q. Brackett, D. E. Morris (1997), ‘The Impact of the Change in Speed Limits on Texas Highways: A Nine-Month Evaluation’ (Texas, USA: Texas Department of Transportation), https://static.tti.tamu.edu/tti.tamu.edu/documents/TTI-1997-8.pdf, accessed 22 October 2022.
Quddus, M. (2013), ‘Exploring the Relationship Between Average Speed, Speed Variation, and Accident Rates Using Spatial Statistical Models and GIS’, Journal of Transportation Safety & Security, 5 (1), 27–45, https://doi.org/10.1080/19439962.2012.705232.
Retting, R. A., M. A. Greene (1990), ‘Effect of the 65-mph speed limit on speeds in three states’, ITE Journal 67 (5), 42–46, https://trid.trb.org/view/483465, accessed 22 October 2022.
Roshandel, S., Z. Zheng, S. Washington (2015), ‘Impact of real-time traffic characteristics on freeway crash occurrence: Systematic review and meta-analysis’, Accident Analysis & Prevention, 79, 198–211, https://doi.org/10.1016/j.aap.2015.03.013.
Russo, B. J., P. T. Savolainen, T. J. Gates (2016), ‘Development of Crash Modification Factors for Installation of High-Tension Cable Median Barriers’, Transportation Research Record: Journal of the Transportation Research Board, 2588 (1), 116–125, https://doi.org/10.3141/2588-13.
Savolainen, P. T., T. J. Gates, B. J. Russo, J. J. Kay (2014), ‘Study of High-Tension Cable Barriers on Michigan Roadways’ (Michigan , USA: Michigan Department of Transportation), RC-1612, https://rosap.ntl.bts.gov/view/dot/28338, accessed 22 October 2022.
Savolainen, P. T., T. J. Gates, Hamzeie, K. R., T. J., Q. Cai (2018), ‘The Interrelationships between Speed Limits, Geometry, and Driver Behavior’ (Ames, IA: Institute for Transportation, Iowa State University), https://intrans.iastate.edu/app/uploads/2018/12/speed_limits_geometry_driver_behavior_interrelationships_w_cvr.pdf, accessed 22 October 2022.
Shirazinejad, R., S. Dissanayake, A. Al-Bayati, D. York (2018), ‘Evaluating the Safety Impacts of Increased Speed Limits on Freeways in Kansas Using Before-And-After Study Approach’, Sustainability, 11 (1), 119, https://doi.org/10.3390/su11010119.
Solomon, D. (1964), ‘Accidents on Main Rural Highways Related to Speed, Driver, and Vehicle ’ (Washington, D.C., USA: United States Burearu of Public Roads), https://safety.fhwa.dot.gov/speedmgt/ref_mats/fhwasa1304/2_40.htm, accessed 22 October 2022.
Streff, F. M., R. H. Schultz (1990), ‘The 65-mph Speed Limit in Michigan: A Second Year Analysis of the Effects on Crashes and Crash Casualties’ (Ann Arbor, MI: The University of Michigan), UMTRI-89-28, https://deepblue.lib.umich.edu/bitstream/handle/2027.42/847/79341.0001.001.pdf, accessed 22 October 2022.
Taylor, M. C., D. A. Lynam, A. Baruya (2000), ‘The effects of drivers’ speed on the frequency of road accidents’ (Berkshire, UK: Transport Research Laboratory), TRL Report 421, https://trl.co.uk/uploads/trl/documents/TRL421.pdf, accessed 22 October 2022.
Upchurch, J. (1989), ‘Arizona’s Experience With the 65-Mph Speed Limit’, Transportation Research Record: Journal of the Transportation Research Board, 1244, 1–6, https://onlinepubs.trb.org/Onlinepubs/trr/1989/1244/1244-001.pdf, accessed 22 October 2022.
Wagenaar, A. C., F. M. Streff, R. H. Schultz (1990), ‘Effects of the 65 mph speed limit on injury morbidity and mortality’, Accident Analysis & Prevention, 22 (6), 571–585, https://doi.org/10.1016/0001-4575(90)90029-k.
Warner, J., H. Chawla, C. Zhou, P. T. Savolainen (2019), ‘Analysis of Rural Interstate Fatality Rates in Consideration of Recent Increases in Maximum Statutory Speed Limits’, Transportation Research Record: Journal of the Transportation Research Board, 2673 (11), 48–58, https://doi.org/10.1177/0361198119851758.
Yu, R., M. Abdel-Aty, M. Ahmed (2013), ‘Bayesian random effect models incorporating real-time weather and traffic data to investigate mountainous freeway hazardous factors’, Accident Analysis & Prevention, 50, 371–376, https://doi.org/10.1016/j.aap.2012.05.011.
Yu, R., M. Quddus, X. Wang, K. Yang (2018), ‘Impact of data aggregation approaches on the relationships between operating speed and traffic safety’, Accident Analysis & Prevention, 120, 304–310, https://doi.org/10.1016/j.aap.2018.06.007.
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Copyright (c) 2022 Nischal Gupta, Megat Usamah Megat Johari, Hisham Jashami, Peter T. Savolainen
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