Contents lists available at ScienceDirect Case Studies on Transport Policy journal homepage: www.elsevier.com/locate/cstp Seatbelt laws and seatbelt use among front- and rear-seat vehicle occupants in fatal crashes in the United States Kwaku F. Boakye a,⁎ , Shashi S. Nambisan b a Transportation Engineer II, Arcadis US Inc., 2839 Paces Ferry Rd SE, Suite 900, Atlanta, GA 30339, United States b Director, Transportation Research Center, Civil Engineering, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Box 454007, Las Vegas, NV 89154-4007, United States ARTICLE INFO Keywords: Seatbelt laws Seatbelt use Front-and rear-seat occupants Tukey-type multiple comparison Crashes ABSTRACT Seatbelt laws are deemed effective at increasing seatbelt use, consequently, reducing fatalities associated with motor vehicle crashes in the United States. Previous studies have provided significant insights about the ef- fectiveness of seatbelt laws, however, studies exploring passenger seatbelt use accounting for the variations in seatbelt laws are not well documented in the literature. Seatbelt laws vary by whether they cover front-seat occupants only or include rear-seat passengers as well. The primary objective of this study was to investigate the differences in adult seatbelt compliance rate based on six categories of seatbelt laws in the United States using crash data. In this present study, six categories of seatbelt laws are considered ranging from no seatbelt law to primary seatbelt law covering all vehicle occupants. Using Tukey-type multiple comparison test, a positive re- lationship between seatbelt laws and adult seatbelt use was found. Specifically, states with stricter seatbelt laws, that is primary law for all front- and rear-seat occupants, exhibit higher seatbelt compliance rate than those with less strict (partial primary/secondary laws) or no seatbelt laws. Given the significant differences in adult seatbelt use based on our study design (using six categories of seatbelt laws), the analysis support that if states upgrade their seatbelt laws from no/secondary laws to primary laws covering all vehicle occupants, there likely will be positive impacts on adult seatbelt use. The findings in this study are to inform and support decision policies and intervention strategies that are effective at promoting safety for motor vehicle occupants. 1. Introduction The prevention of injuries associated with motor vehicle crashes is an important public health concern in the United States (U.S.). In 2017, there were an estimated 6.4 million police-reported motor vehicle crashes in the U.S., resulting in 37,133 fatalities and 2.74 million people injured (National Center for Statistics and Analysis, 2019a). Majority of road fatalities are attributed to human factors including speeding, driving impaired or distracted and seatbelt nonuse (Blincoe et al., 2010). Studies have shown that the seatbelt is one of the most effective devices that can be used to reduce the severity of injuries in crashes (Blincoe et al., 2010; Lee and Schofer, 2003; National Center for Statistics and Analysis, 2018). The National Highway Traffic Safety Administration (NHTSA) estimates that seatbelts can reduce the risk of fatal injuries to front-seat car passengers by 45% and moderate-to-cri- tical injuries by 50% (National Center for Statistics and Analysis, 2018). Despite the safety benefits of seatbelts, a significant proportion of passengers still travel unrestrained. In 2017, among the fatally injured passenger vehicle occupants in the U.S., approximately 43% were known to have not used a seatbelt (National Center for Statistics and Analysis, 2019a). Seatbelt use rates in the U.S. have increased over the past three decades since the first seatbelt law was adopted by New York in 1984. Belt use reached 75% nationwide in 2002, the highest rate since a comprehensive national survey was first conducted in 1994 with use rate at 58% (Glassbrenner, 2002). In 2018, nationwide seatbelt use rate was at 90% (Enriquez and Pickrell, 2018). Despite the increase, seatbelt use rates still vary widely among states. For example, seatbelt use in 2017 ranged from as low as 67.6% in New Hampshire to as high as 97.1% in Georgia. Although multiple factors such as seatbelt tech- nology designs, socio-demographic characteristics, and other unknown factors account for the disparities in seatbelt use among states, the impact of seatbelt legislation cannot be overemphasized. Past studies have demonstrated that mandatory seatbelt laws combined with media campaigns are effective at increasing seatbelt use (Shults et al., 2004a; Beck and Shults, 2009; Beck et al., 2007; Harper and Strumpf, 2017; https://doi.org/10.1016/j.cstp.2020.04.003 Received 17 November 2019; Received in revised form 19 March 2020; Accepted 13 April 2020 ⁎ Corresponding author. E-mail addresses: Kwaku.Boakye@arcadis.com (K.F. Boakye), Shashi@unlv.edu (S.S. Nambisan). Case Studies on Transport Policy xxx (xxxx) xxx–xxx 2213-624X/ © 2020 World Conference on Transport Research Society. Published by Elsevier Ltd. All rights reserved. Please cite this article as: Kwaku F. Boakye and Shashi S. Nambisan, Case Studies on Transport Policy, https://doi.org/10.1016/j.cstp.2020.04.003