Research Article ABehavioralModelofDrivers’MeanSpeedInfluencedbyWeather Conditions, Road Geometry, and Driver Characteristics Using a Driving Simulator Study Mehdi Zolali ,BabakMirbaha ,MaziyarLayegh ,andHamidRezaBehnood Civil Engineering Department, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran Correspondence should be addressed to Babak Mirbaha; mirbaha@eng.ikiu.ac.ir Received 7 January 2021; Revised 5 April 2021; Accepted 27 April 2021; Published 22 May 2021 Academic Editor: Yu-Cheng Lin Copyright © 2021 Mehdi Zolali et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Driving above the speed limit is one of the factors that significantly affect safety. Many studies examined the factors affecting the speed of vehicles in the simulated environment. e present study aimed to analyze drivers’ characteristics, time and weather conditions, and geometric features’ effect on mean speed in simulated conditions simultaneously. In this regard, the simulator experiment data of 70 drivers were collected in a two-lane rural highway at six different times, and weather scenarios and their socioeconomic characteristics were collected by a questionnaire. Structural equation modeling (SEM) was used to capture the complex relationships among related variables. Eleven variables were grouped into four latent variables in the structural model. Latent variables including “Novice Drivers,” “Experienced Drivers,” “Sight Distance,” and “Geometric Design” were defined and found significant on their mean speed. e results showed that “Novice Drivers” have a positive correlation with the mean speed. Meanwhile, “Experienced Drivers,” who drive 12% slower than the novice group, negatively affect the mean speed with a standard regression weight of −0.08. is relation means that young and novice drivers are more inclined to choose higher speeds. Among variables, the latent variable “Sight Distance” has the most significant effect on the mean speed. is model shows that foggy weather conditions strongly affect the speed selection behavior and reduce the mean speed by 40%. Nighttime also reduces mean speed due to poor visibility conditions. Furthermore, “Geometric design” as the latent variable indicates the presence of curves on the simulated road, and it can be concluded that the existence of a curve on the road encourages drivers to slow down, even young drivers. It is noteworthy that the parts of the simulated road with a horizontal curve act as a speed reduction tool for drivers. 1.Introduction Driving above the speed limit is one of the most critical issues in safety studies, increasing collision risk. Besides, it plays a significant role in the cost and severity of accidents. World Health Organization reported that an increase in mean speed is directly related to the likelihood of a crash occurring and its consequences; for example, a rise of 1 km/h in mean vehicle speed increases 3% and 4-5% in the inci- dence and fatality of crashes, respectively [1]. us, re- searchers have a great deal of interest in evaluating the factors affecting the drivers’ speed. A wide variety of factors have been studied concerning drivers’ speed choice and mainly divided into environmental characteristics, drivers’ behavior and characteristics, and weather and time condition. Some studies evaluated the effects of geometric and roadside features on vehicles’ speed using a driving simulator [2–7]. In this regard, Bella [2] considered the effect of three different roadside conditions and two cross-sections on drivers’ speed in a two-lane highway. e collected data for 36 drivers indicated that roadside configuration influ- ences lateral position without any role for driving speed. Goralzik and Vollrath [3] defined different scenarios based on the differences in roadway curvature, lane width, speed limit, and passengers’ number in the car to evaluate drivers’ speed choice. e findings indicated that speed limitation and road geometry have the most substantial effects on drivers’ speed choice. Furthermore, Sadia et al. [4] inves- tigated the effect of different environmental and road characteristics (such as horizontal and vertical curves and Hindawi Advances in Civil Engineering Volume 2021, Article ID 5542905, 18 pages https://doi.org/10.1155/2021/5542905