Factors associated with driver injury severity of motor vehicle
crashes on sealed and unsealed pavements: Random parameter
model with heterogeneity in means and variances
Ihsan Obaid a,b, Ali Alnedawi c,⇑, Ghufraan Mohammed Aboud d, Reuben Tamakloe e,
Hamsa Zuabidi a,b, Subasish Das f
a School of Civil and Construction Engineering, Oregon State University, Corvallis, OR 97331-3212, United States
b Roads and Transport Department, College of Engineering, University of Al-Qadisiyah, Iraq
c Diwan Endowment, Baghdad, Iraq
d Highway and Transportation Engineering Department, Mustansiriyah University, Baghdad, Iraq
e Department of Transportation Engineering, The University of Seoul, Seoul 02504, South Korea
f Texas A&M Transportation Institute, 1111 RELLIS Parkway, Bryan, TX 77807, United States
a r t i c l e i n f o
Article history:
Received 16 August 2021
Received in revised form 28 March 2022
Accepted 9 April 2022
Available online xxxx
Keywords:
Road surface type
Injury severity
Mixed logit model
Heterogeneity in mean and variance
Random parameter
a b s t r a c t
The effect of sealed or unsealed road pavements on motorist’s injury severities has not
been extensively explored. This study collected a four-year crash dataset (2015–2018)
from South Australia to explore this issue. The data shows 3,812 and 1,086 crashes at
sealed and unsealed pavement surfaces, respectively, during those years. This study examines
the consequence of sealed and unsealed pavements on driver injury severity outcomes
of motor vehicle crashes. A mixed logit model was developed by accounting for heterogeneity
in means and variances of the random parameters. The variables were distributed
among several categories: driver, temporal, spatial, roadway characteristics, crash type,
vehicle type, and vehicle movement. Four random parameters were observed in the sealed
model, whereas five parameters were in the unsealed one. Moreover, the sealed pavements
model showed substantial heterogeneity in means of four of the random parameters, while
the unsealed pavements model has some heterogeneity in both means and variances of
some of the random parameters. Marginal effect results indicate that two indicator variables
have enlarged the likelihood of driver severe injury consequences in sealed, alcohol
involvement and posted speed limit > 100 km/hr. Additionally, four other significant variables
sustain the probability of severe injury outcomes at unsealed pavement like male drivers,
middle-aged drivers, rollover crash types, and crashes at straight roads. Based on
these variables, various countermeasures were recommended to enhance the safety of both
types of pavements.
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This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/
licenses/by-nc-nd/4.0