Ahmed Abdel-Rahim

Microscopic Modeling of Traffic Signal Operations: Comparative Evaluation of Hardware-in-the-Loop and Software-in-the-Loop Simulations

Currently, there are three different methods to model traffic signal operations in microscopic simulation models: the simulation models controller emulator, hardware-in-the-loop simulation, and software-in-the-loop simulation. Although all three methods can be based on the same industry standard code, their different implementations suggest potential operational differences. This study investigates operational differences of the three methods by examining how each method operates in five experimental scenarios. Each of the scenarios differs from the others in network size (one intersection to five intersections) and operational strategies (pretimed, actuated, actuated–coordinated, and two different signal transition logics). Ten 75-min simulation runs with 100-ms simulation resolution were executed for each experiment with the three signal control modeling alternatives. The results showed that for basic signal control operations, such as pretimed and isolated actuated operations, the three alternatives provided similar results as indicated by the average green time allocation and different operational measures of effectiveness. When advanced controller operations were used, such as signal transition logic, the simulation model emulator showed significantly different behavior than that observed in hardware-in-the-loop and software-in-the-loop simulations.

Potential crash reduction benefits of shoulder rumble strips in two-lane rural highways

This paper reports the findings from a study aimed at examining the effectiveness of shoulder rumble strips in reducing run-off-the-road (ROR) crashes on two-lane rural highways using the empirical Bayes (EB) before-and-after analysis method. Specifically, the study analyzed the effects of traffic volume, roadway geometry and paved right shoulder width on the effectiveness of shoulder rumble strips. The results of this study demonstrate the safety benefits of shoulder rumble strips in reducing the ROR crashes on two-lane rural highways using the state of Idaho 2001-2009 crash data. This study revealed a 14% reduction in all ROR crashes after the installation of shoulder rumble strips on 178.63miles of two-lane rural highways in Idaho. The results indicate that shoulder rumble strips were most effective on roads with relatively moderate curvature and right paved shoulder width of 3 feet and more.

A combined approach to ITS vulnerability and survivability analyses

We now live in a digital society where day-to-day operations are optimized by complex real-time control systems. Our surface transportation infrastructure has evolved to a level of complexity where intelligent transportation systems (ITS) are essential for large urban environments. Our surface transportation infrastructure is a highly complex system subject to day-to-day operations with different levels of recurring congestion, stresses from special events, and damage from natural disasters, accidents, sabotage, and nuisance attacks. Under normal traffic conditions, ITS operation is optimized for system-wide objective functions (i.e., minimize network-wide delay or maximize throughput), and travelers modify their behavior accordingly by alternating their departure time, travel route, or mode of travel. This work presents a security and survivability analysis of the City of Moscow, Idaho ITS project, which is now under development.

Process for Improving Design of Transportation Curriculum Materials with Examples

Student-centered learning is presented as an alternative to the traditional lecture-based approach commonly used in transportation engineering education. Student-centered learning includes an array of pedagogical approaches, such as active learning, cooperative learning, problem-based learning, guided discovery, applied critical thinking, and open-ended labs, each promoting deeper levels of understanding. Two methods of curriculum development that support student-centered learning are presented. Three examples of transportation curricula based on these two methods are offered: the Highway Capacity Manual Applications Guide, mobile signal timing training, and the Transportation Education Development Pilot Project Arterial Traffic Signal Operations course. Each example is evaluated according to criteria that support the curriculum development methods. Conclusions from this evaluation and suggested future research directions are presented.

Traffic Signal Operations Education Through Hands-On Experience: Lessons Learned from a Workshop Prototype

The development, implementation, and assessment of the traffic signal summer workshop (TSSW) are explored. An innovative educational prototype that has been conducted at the University of Idaho during the past two summers, TSSW addresses several critical issues, including the need to educate and train university engineering students in different ways, and the lack of adequately trained engineers and technicians prepared to design and manage today’s traffic signal infrastructure. Those issues are discussed along with the pedagogical basis for hands-on experiences in engineering education. Also discussed is how the university has responded, with the TSSW prototype, to the need to deliver transportation engineering education in a new way.

Modeling advanced traffic signal control systems: a communication network prototype

This paper discusses the development of a microprocessor based hardware design as a solution to the need for automated ITS network configuration for differing modes of traffic controller operation. The design, called the controller interconnection network (CIN), was required to be scalable in a number of traffic controllers and permit multimode operation. The design allows remote control of some operations via a Web-based interface.

A survivable critical infrastructure control application

A microcontroller-based system is described that utilizes real-time distributed sensor data to adapt a critical infrastructure control application to reflect current environment conditions. The system monitors the behavior of its software execution based on real-time analysis of certified frequency spectra and call-graph transition validations in order to detect and react to uncertified behavior and state transitions. The real-time data used to adapt the application is geographically distributed and redundant. The overall system is outlined with focus on the contingency management of the system. Finally, a basic reliability analysis is given as a tool to evaluate the impact of fail rate assumptions.

A measurement-based design and evaluation methodology for embedded control systems

A measurement-based design and evaluation methodology for embedded control systems is presented that features 1) better control of executions through reduction of non-determinism, 2) certified behavior of executions, 3) real-time monitoring of operations, functionalities and modules, which 4) allows adaptation to non-certified behavior. Using principles of Design for Survivability the software system is broken down into costatements (the unit of execution in Dynamic C) with low degree of non-determinism in their executions. This results in a significant increase in the accuracy of run-time profiling, which in turn achieves potential for better detection of deviation from certified executions. The formal model to achieve these goals is introduced and the effectiveness is demonstrated in a real control

Assessing Surface Transportation Network Component Criticality: A Multi-Layer Graph-Based Approach

As critical infrastructure, surface transportation networks need to be designed not only for safety and efficiency but also for maximum survivability during extreme events such as accidents, natural disasters and malicious events. Surface transportation systems are increasingly dependent on an extensive network of detection, surveillance, communication, and computing devices. It is no longer sufficient to consider the analysis of the transportation network, its components, its communication infrastructure, and its power supply in separation. This paper explores the use of multi-layer graph-based analysis applied to assess surface transportation network component criticality. Three layers of critical infrastructure are analyzed: power, communication, and physical roadway network. Interactions within layers and between layers are identified and the relative criticality of each component in the three layers is quantified as to the components essentiality in terms of network performance. The analysis provides a simple means of assessing the importance of different components in critical infrastructure layers allowing decision makers to prioritize threat mitigation alternatives.

A case study of critical point identification in the physical and communication layers of a small urban transportation system

Surface transportation is an important critical infrastructure as it provides the essential services that highly impact a nations economy. It is important to identify and protect the essential components of the transportation system to ensure its survivability. This paper describes critical point identification of a small urban intelligent transportation network. The analysis was conducted for two layers: physical/control and communication layers. Microscopic simulation modelling was used to identify critical points in the physical/control layer. The critical point identification of the communication layer was done using graph metrics such as hop counts and dependencies. A final node ordering with regard to both layers is then obtained using the criticality values identified for each layer. The critical point identification approach presented in this paper provides transportation professionals with a tool to identify critical nodes that need to be strengthen and hardened to achieve a survivable transportation network.