Evaluation of CORSIM car-following model by using global positioning system field data

It has been recognized that CORSIM (and its constituent program, NETSIM) is one of the most widely used and effective computer programs for the simulation of traffic behavior on urban transportation networks. It popularity is due in large part to the high level of detail incorporated into its modeling routines. However, the car-following models, used for the simulation of driver behavior in the program, have not been formally calibrated or validated. Since the model has performed well in a wide range of applications for so many years, it has always been assumed to have an implied validity. This study evaluated the NETSIM car-following models by comparing their results with field data. Car-following field data were collected using a new data collection system that incorporates new Global Positioning System and geographic information system technologies to improve the accuracy, ease, speed, and cost-effectiveness of car-following data collection activities. First, vehicle position and speed characteristics were collected under field conditions. Then simulated speeds and distances were based on identical lead vehicle actions using NETSIM car-following equations. Comparisons of simulated and field data were completed using both graphical and statistical methods. Although some differences were evident in the graphical comparisons, the graphs overall indicated a reasonable match between the field and simulated vehicle movements. Three statistical tests, including a goodness-of-fit test, appear to support these subjective conclusions. However, it was also found that definitive statistical conclusions were difficult to draw since no single test was able to compare the sets of speed and distance information on a truly impartial basis

Existing and potential methodologies for evaluating in-use safety performance of roadside safety equipment

This paper summarizes the findings of a recent review of practice-and research-methods related to the In-service Performance Evaluation (ISPE) of roadside safety equipment installation and, more specifically, guardrail end treatments. The review was necessitated by the need for state agencies to measure performance of roadside safety hardware beyond crash tests. It focused on guidance for the field collection of data and analytical methods related to agency ISPE process goals. It encompassed both road safety literature for existing methods as well as research studies from other fields to identify methods that may also have the potential to be applied by state departments of transportation to enhance their ISPE process. This paper summarizes the three primary areas, including 1.) Existing ISPE processes and goals; 2.) Research designs and analysis techniques for observational data analysis; and 3.) Practices of rare-event analysis from other fields of study. The review also showed that analysis objectives and methods are influenced by the cost, time, and effort to collect data to implement the methodology, but that other sources of road/crash characteristics not commonly used in ISPE studies like roadway crash databases can be valuable input to the ISPE process. In terms of rare event analysis work from other fields, it was found that most of the existing identification, assessment, modeling, forecasting, and classification techniques from other areas of study currently have limited potential for application in the ISPE of guardrail end treatments. However, as sensor technologies evolve and enhance the ability to monitor infrastructure and archive large safety data with higher reliability and lower cost, some of these techniques can become part of the ISPE process

Validation Techniques for Region-Level Microscopic Mass Evacuation Traffic Simulations

The experiences of several recent evacuations have demonstrated how a mass evacuation of a major city can affect traffic throughout an entire region. This realization has brought the need for analyzing and evaluating evacuation plans at a regional level. Numerous recent studies have devoted themselves to the topic of simulating large-scale evacuations. However, few studies have developed procedures for the validation of large-scale models. This paper discusses validation within the context of the recent development of the regional multimodal evacuation model for New Orleans, Louisiana. The New Orleans model is unique because it is among the first ever to incorporate qualitative and quantitative model validation procedures based on field data collected during an actual mass evacuation. The paper discusses the various statistics considered for validation, including their inherent advantages and disadvantages. It also presents the results obtained from the validation exercises of the New Orleans model. The study concluded that regression analyses were the most appropriate for statistically analyzing the spatial and temporal data correlations between the traffic patterns produced within the simulation and those actually observed during the Hurricane Katrina evacuation. From a qualitative standpoint, colorized spatiotemporal maps were also found to be quite effective for visualizing traffic speed and volume patterns. The maps were also invaluable for quickly identifying and analyzing bottleneck areas at both the local and regional levels

Modeling and analysis of evacuation contraflow termini

Over the last five years, the Department\u27s of Transportation in 12 coastal states threatened by hurricanes have developed plans for the implementation of contraflow traffic operations on freeways during evacuations. Contraflow involves the use of one or more inbound travel lanes for the movement of traffic in the outbound direction. It is both a logical and cost effective strategy because evacuation traffic can be loaded into underutilized inbound lanes, thereby significantly increasing outbound capacity without the need to construct additional lanes. This paper summarizes the results of two recent studies to evaluate the implications of contraflow evacuations on freeways. The research focused on what are widely regarded to be the most critical locations of contraflow segments, the initiation and termination points. The termini configurations are important because they effectively dictate the capacity of these segments because they control how many vehicles can get in and out In the research, traffic simulation models were developed to simulate the operation of planned configurations under varying levels of traffic demand to assess their operating characteristics. The results showed that many of the current designs of the initiation and termination points will likely restrict the ability of these segments to be used to their maximum effectiveness. Another key finding was the extent to which the spatial and/or temporal spreading of traffic demand can yield significant benefits to the overall effectiveness of contraflow freeway evacuations. It is hoped that with an increased awareness of these issues, these findings can be used to enhance the effectiveness of existing evacuation plans

From normal operation to evacuation: Single-vehicle safety under adverse weather, topographic, and operational conditions

The negative effects of weather (e.g., strong winds, snow, and icy rain) on the safety of vehicles have been recognized and reported upon for some time worldwide. As an important category of vehicle accidents, the single-vehicle noncollision accident has not been studied sufficiently under adverse environmental and topographic conditions. In the United States, strong wind, together with other adverse weather and topographic conditions, has been blamed for many single-vehicle accidents every year, especially those involving trucks. Vehicle safety not only threatens people\u27s lives during normal operations, but may even put many people in miserable situations when an emergency evacuation is interrupted by frequent accidents on key routes. As a result, the safety of many people who are delayed in congestion on evacuation routes may be jeopardized. The reasons that cause single-vehicle accidents can be very complicated: from a single primary reason such as strong wind gusts to the combination of several reasons such as weather conditions, vehicle conditions, road surface conditions, driver operational errors, etc. This study seeks to investigate the safety of vehicles during normal operations as well as emergencies through replicating the natural environments. It starts with a brief overview of single-vehicle accidents caused by environmental and topographic conditions around the United States in normal operations, followed by discussions about the current challenges existing in the evacuation practices. An attempt is then made to model the complicated weather, road surface, and driver operational process, such as rain, snow, camber, grade, and acceleration/deceleration as well as steering processes. With the proposed accident assessment framework, the accident-related response is studied and accident risks are assessed for vehicles. The study may also provide a useful basis for traffic designs on highways with complicated topographic and weather conditions and optimization of evacuation routes and strategy with minimized single-vehicle accident risks. © 2009 ASCE