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Article

Evaluating the Safety Impacts of Increased Speed Limits on Freeways in Kansas Using Before-And-After Study Approach

1
Department of Civil Engineering, Kennesaw State University, 655 Arnston Drive, Marietta, GA 30062, USA
2
Department of Civil Engineering, Kansas State University, 2118 Fiedler Hall, Manhattan, KS 66506, USA
3
Kimmel School of Construction Management, Western Carolina Univ., Cullowhee, NC 28723, USA
*
Author to whom correspondence should be addressed.
Sustainability 2019, 11(1), 119; https://doi.org/10.3390/su11010119
Received: 19 November 2018 / Revised: 10 December 2018 / Accepted: 22 December 2018 / Published: 26 December 2018
(This article belongs to the Special Issue Sustainable Transport Safety)
In the summer of 2011, a change in the Kansas laws came into effect, increasing the speed limit on a selected set of freeway sections from 70 mph to 75 mph. Higher speeds were thought to have economic benefits, mostly because the travel time reduction means people reach their destinations more quickly. In this study, the sections where the speed limits remained unchanged, are compared to freeway sections that have been influenced by speed limit increase, to evaluate safety effectiveness. The study utilizes the before-and-after study with comparison group method to assess the safety effects provided in the Highway Safety Manual (HSM). Two crash datasets, obtained by considering three years before and three years after the speed limit increase, were compared in order to evaluate the safety effects of the speed limit change. The crash modification factors (CMFs) were estimated, which showed that there was a 27% increase in total crashes and a 35% increase in fatal and injury crashes across all sections after the speed limit change, and these increases were statistically significant at 95% confidence level. These confounding results show that the speed limit increase has not been beneficial for traffic safety in Kansas, and hence it is important to be cautious in such future situations. Also, additional data have been presented which would be beneficial in identifying and understanding any behavior change in drivers following a speed limit increase. View Full-Text
Keywords: speed limit increase; before-after study; fatal and injury crashes; freeways; safety evaluation; crash modification factors speed limit increase; before-after study; fatal and injury crashes; freeways; safety evaluation; crash modification factors
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MDPI and ACS Style

Shirazinejad, R.S.; Dissanayake, S.; Al-Bayati, A.J.; York, D.D. Evaluating the Safety Impacts of Increased Speed Limits on Freeways in Kansas Using Before-And-After Study Approach. Sustainability 2019, 11, 119. https://doi.org/10.3390/su11010119

AMA Style

Shirazinejad RS, Dissanayake S, Al-Bayati AJ, York DD. Evaluating the Safety Impacts of Increased Speed Limits on Freeways in Kansas Using Before-And-After Study Approach. Sustainability. 2019; 11(1):119. https://doi.org/10.3390/su11010119

Chicago/Turabian Style

Shirazinejad, Reza S., Sunanda Dissanayake, Ahmed J. Al-Bayati, and David D. York 2019. "Evaluating the Safety Impacts of Increased Speed Limits on Freeways in Kansas Using Before-And-After Study Approach" Sustainability 11, no. 1: 119. https://doi.org/10.3390/su11010119

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