Ghulam H Bham

Driving simulator validation of driver behavior with limited safe vantage points for data collection in work zones

INTRODUCTION This study is aimed at validating a driving simulator (DS) for the study of driver behavior in work zones. A validation study requires field data collection. For studies conducted in highway work zones, the availability of safe vantage points for data collection at critical locations can be a significant challenge. A validation framework is therefore proposed in this paper, demonstrated using a fixed-based DS that addresses the issue by using a global positioning system (GPS). METHODS The validation of the DS was conducted using objective and subjective evaluations. The objective validation was divided into qualitative and quantitative evaluations. The DS was validated by comparing the results of simulation with the field data, which were collected using a GPS along the highway and video recordings at specific locations in a work zone. The constructed work zone scenario in the DS was subjectively evaluated with 46 participants. RESULTS The objective evaluation established the absolute and relative validity of the DS. The mean speeds from the DS data showed excellent agreement with the field data. The subjective evaluation indicated realistic driving experience by the participants. PRACTICAL APPLICATIONS The use of GPS showed that continuous data collected along the highway can overcome the challenges of unavailability of safe vantage points especially at critical locations. Further, a validated DS can be used for examining driver behavior in complex situations by replicating realistic scenarios.

A Simple Lane Change Model for Microscopic Traffic Flow Simulation in Weaving Sections

Abstract This paper presents the development and validation of a simple microscopic traffic simulation model for driver lane change behavior in freeway weaving sections. The simple model, called the weaving model, is computationally efficient and requires fewer calibration parameters. The models calibration parameters can be found from the field data which makes the calibration process simpler compared to more detailed simulation models. Two types of lane change logics were developed: a) discretionary and b) mandatory. Discretionary lane change logic considers a drivers dissatisfaction with his/her current speed and feasibility of speed gain in the target lane. A mandatory lane change is performed for vehicles exiting, entering or moving to a preferred lane on the highway. The weaving model was validated at the microscopic level by comparing the trajectories of vehicles from simulation with the field data, whereas macroscopic validation was performed using statistical and error tests for average speed and section density. Lane change frequency from the proposed model was also compared with the field data and good agreement was observed. The results from the proposed model were compared with two popular simulation models, VISSIM and AIMSUN, which indicated that the proposed model performed at least as good as these models.

Statistical Models for Preferred Time Headway and Time Headway of Drivers in Steady State Car-Following

This paper proposes two shifted continuous distribution models for preferred time headway (Tp) and time headway in steady state car-following (Tws), i.e. the lognormal and gamma models. Lognormal distribution with a shaft of 0.21 seconds provides a good fit to Tp, whereas a shift of 0.26 is proposed to Tws. Similarly, shifted Gamma distribution is proposed for Tp and Tws with shifts of 0.21 seconds and 0.26 seconds, respectively. Detailed data sets (FHWA Data) observed at one-second intervals collected from aerial photography for four sites have been used in this paper. The data sites are a basic freeway section, a ramp merge, a lane drop and a ramp weave section. Tp and Tws were found to be the shortest (mean, median and st. dev.) on ramp weave section compared to all other sites. It was also found that the shifted Lognormal distribution provided a better fit to all the observed sites compared to the shifted Gamma distribution.

Longitudinal Evaluation of a GIS Laboratory in a Transportation Engineering Course

This paper focuses on the potential impact of student-centered feedback for enhancing the learning experience of civil engineering students that used a geographic information system (GIS) based tutorial in a transportation engineering course. The tutorial was implemented in a laboratory environment developed as a self-guided activity supported by a web-based learning system. The formative research proposed in this study includes a series of four successive implementations of this laboratory. Students’ performance, beliefs, and perceptions were monitored by using a mixed-methods design approach and weaknesses identified from early implementations were addressed before the next implementation of the laboratory activity. The students’ performance was found to improve when the GIS web-based tutorial was complemented with an instructor-driven short introduction that anchored the laboratory activity in traffic safety. In addition, students’ feedback in both quantitative and qualitative format indicated weakness...

Younger Driver's Evaluation of Vehicle Mounted Attenuator Markings in Work Zones Using a Driving Simulator

Abstract This paper evaluates the effectiveness of four vehicle mounted attenuator (VMA) markings used by the Departments of Transportation (DOTs) in work zones. A driving simulator was used to evaluate the perception of seventy-three young participants who drove through virtual highway work zones. Lane change distance (LCD) was used to analyze their reaction to the VMA markings during the daytime. An analysis of variance (ANOVA) was performed to determine the significant variables affecting the LCD. A pairwise least-square means test was performed to determine the difference between the LCDs for the markings. A subjective evaluation was also carried out in which the participants ranked the markings based on different criteria. The participants were also surveyed on the features of individual markings, and their most preferred marking. The results of the objective and subjective evaluations were consistent, and suggested that overall the red and white checkerboard pattern was the most effective and preferred among the four markings. A DOT survey conducted in conjunction with this study indicated that the yellow and black inverted ‘V’ pattern was widely used in the United States as it was provided by most VMA suppliers.

An evaluation of performance measures for hotspot identification

ABSTRACT An important step in highway safety analysis is the identification of high-crash locations or “hotspots.” Various performance measures are currently used for hotspot identification (HSID). Current measures are mostly based on crash frequency. This article proposes a performance measure based on crash severity, namely, the crash factor measure (CFM). In this article, the performance measures are classified broadly by crash frequency and crash severity. The crash severity measures, the CFM, the equivalent property damage only (EPDO), and the Empirical Bayes supplemented with crash severity (EBCS), and the crash frequency measures, the crash rate (CR) and the Empirical Bayes (EB) are evaluated using eight tests based on empirical and simulated data. To ensure detailed assessment, the evaluation was carried out for three entire highway routes (an Interstate, a US, and a State highway), that is, beyond the top 1% to 10% of hotspots commonly examined. The results from the evaluation demonstrate that the EB and CFM measures performed consistently and are recommended for use. Based on inconsistent results, the CR measure is not recommended for HSID. Based on the overall results, it is also recommended that, for any proposed performance measure, the evaluation should be carried beyond 1% to 10% of the hotspots.

Safety Effect of Missouri's Strategic Highway Safety Plan

This study systematically evaluated the changes in motor vehicle crashes that occurred on the Missouri Interstate highway system following the implementation of the Missouri Strategic Highway Safety Plan (MSHSP) between 2004 and 2007. The MSHSP implemented crash injury reduction strategies in enforcement, education, engineering, and public policy. Empirical Bayesian methods were commonly used to evaluate the effects of any change in safety as a result of countermeasures. This paper presents a simple new approach to evaluating the effects of Missouris safety plans on roadway crashes. For crash data associated with traffic and roadway characteristics, negative binomial regression models were developed for the before-through-change conditions using a variable that was set to zero for preimplementation years and gradually increased over the implementation years to reach a plateau at the conclusion of the safety plans. The models developed for the various collision types and crash severities were used to estimate the expected number of crashes at roadway segments in 2008, assuming with and without the implementation of MSHSP. This procedure estimated significant reductions of 10% in the overall number of crashes and a 30% reduction for fatal crashes. Reductions in the number of collision types were estimated to be 18% to 37%. The theoretical results indicated that the MSHSP was a successful policy in reducing the number of crashes and decreasing fatalities by reducing the most severe collision types such as head-on crashes. The results are also consistent with many international studies and suggested that the safety strategic plans should be promoted as an effective treatment for highways.

Identification of Crash-Contributing Factors: Effects of Spatial Autocorrelation and Sample Data Size

Sample sets of crash data are used to examine the similarities in crash-contributing factors among various counties in the state of Arkansas that have similar effects on spatial autocorrelation. Morans I and Getis–Ord Gi* statistics were used to determine the correlation, and multinomial logistic regression was used to identify the crash-contributing factors. Seventy-five counties were divided into five categories on the basis of the Z-values of the Getis–Ord Gi* statistic. Depending on the sample data size, for each category crash data from a county or a group of counties were used, and crash-contributing factors were identified on the basis of the crash severity index. Results indicated that most of the crash-contributing factors identified for each category were also identified by the sample crash data from a county or a group of counties in that category. Pulaski County, with the highest Z-value from the first category, had the largest cluster of crashes and identified the highest percentage (55%) of factors that contributed to crashes in the category by using the sample crash data. From the sample data used, the multinomial logistic regression indicated the following factors to be positively associated with crash severity: nighttime driving, driving under the influence of alcohol, roadway gradient, alignment on a curve, rural areas, and collision types head-on and sideswipe-same-direction. The results of this research can be used for better allocation of funds by departments of transportation by analyzing smaller sets of data to identify crash-contributing factors associated with higher levels of crash severity.

Measuring traffic congestion using space occupancy in real time for ITS applications

The paper presents space occupancy (So~) as a measure of state of traffic congestion in real time. To accurately measure state of traffic, space occupancy (Sor is calculated as the percentage length of highway occupied by vehicles, taking into account length of every vehicle. The paper presents the concepts of Soc and describes the usefulness of utilizing Sor compared to density. The relationship between So~ and density is also determined and a traffic simulation model CELLSIM is used to evaluate the accuracy of each parameter. The parameters were studied using different length of vehicles and mix of traffic. So~ more accurately determines the magnitude of congestion and may be used to set accurate thresholds of traffic congestion. The concepts described can be applied to incident detection in real time control of network traffic flow in Intelligent Transportation Systems.

Application of Threshold Concepts to Improve a Design-Focused Course in Transportation Engineering

Design is an integral part of engineering courses. To address its associated problems, however, is a challenging task in instruction because of designs open-endedness and complexity. In this study, two theoretical models were implemented in an introductory transportation engineering course to address the challenges associated with design of a highway. First, the theoretical framework proposed by the threshold concepts model was used to identify a candidate concept for the instructional redesign process. Two major characteristics of threshold concepts, integrativity and transformativity, were used to identify horizontal alignment as a candidate concept for the highway design process. Second, concept mapping was done to create operational measures of the integrativity of complex concepts, such as horizontal alignment. These maps and measures led to several changes to the structure of lecture materials and project tasks. Finally, questions for reflective assessment were administered to students after each redesigned instructional task and at the end of the course to find evidence of the potential transformativity of the proposed instructional changes. Implementation of the above-mentioned theoretical framework allowed the instructor who participated in the study to successfully streamline the instructional process and benefitted student perceptions and attitudes about learning highway design.