The past few years have seen a rapid evolution in the sophistication of traffic microsimulation models and a consequent major expansion of their use in transportation engineering and planning practice. Researchers and practitioners have employed an extensive array of approaches to calibrate these models and have selected a wide range of parameters to calibrate and a broad range of acceptance criteria. A methodical, top-down approach to model calibration is outlined; it focuses the initial effort on a few key parameters that have the greatest impact on model performance and then proceeds to less critical parameters to finalize the calibration. A three-step calibration/validation process is recommended. First, the model is calibrated for capacity at the key bottlenecks in the system (the capacity calibration step). Second, the model is calibrated for traffic flows at nonbottleneck locations in the system (the route choice calibration step). Finally, the overall model performance is calibrated against field-measured system performance measures such as travel time and delay (the system performance calibration step). This three-step process is illustrated in an example application for a freeway/arterial corridor.
Existing simulation models have difficulty in accurately modeling oversaturated traffic conditions on freeways. A new behavioral algorithm for oversaturated freeway flow can be used in microscopic simulation models; it was developed as part of the Next Generation Simulation (NGSIM) project, sponsored by FHWA. The proposed algorithm is an integrated car-following and lane-changing modeling framework that is consistent with the kinematic wave theory. The algorithm can explicitly model mandatory and discretionary lane changing, including cooperation during lane changing. As an extension of the algorithm, a new on-ramp merging model was developed and incorporated into the model. The proposed algorithm also accounts for the relaxation process following lane changing. The proposed model includes a small number of parameters that can be readily measured in the field. The proposed model was implemented into a microscopic simulator, and it was validated with both vehicle trajectory data and macroscopic detector data from an NGSIM test site. The results show good agreement with real-world traffic behavior. The study products, including an algorithm description, analysis results, and computer code, are documented and made available to developers and users of traffic simulation tools.
This study proposes a mixed traffic simulation framework that integrates vehicle car‐following (CF) and lane‐changing (LC) with connected and automated vehicles (CAVs) of different cooperation behaviors. This framework is centered at a CAV LC model incorporated with CF dynamics in mixed traffic. The model was calibrated and validated using data collected from small‐scale field experiments in a previous study. To demonstrate a large‐scale application of this framework, PTV Vissim was used to implement the framework on a segment of Interstate 75 highway. Sensitivity analyses were conducted to investigate the impacts of key parameters on traffic mobility and stability performance. The results show that traffic performance degraded as the traffic demand and vehicle diverging rate increased. As the CAV penetration rate increased, traffic performance fluctuated when CAVs were more conservative. As the CAV cooperation rate, incentive criterion threshold, and incentive criterion bias increased, mobility and stability performance first improved and then degraded. When CAV platooning was considered, traffic performance was enhanced. These findings shed light on mixed traffic management from the perspectives of both transportation operators (e.g., facilities and policies to promote vehicle cooperation) and automakers (e.g., tuning parameters in their LC models) to achieve the best traffic performance.
The multimodal expressway system is a concept of introducing travel choices for suburban commuters in major metropolitan areas relatively quickly and inexpensively. The entire existing limited-access highway system would provide for free flow of carpool vehicles and buses by temporarily slowing (or stopping) and releasing excess traffic at freeway entrance ramps and on the freeway main line at a series of concentric cordon locations around the core of the metropolitan area. At these locations, travel lanes would be created on the shoulder and restricted to use by buses and high-occupancy vehicles with three or more persons and would allow them to bypass the slower moving metered general-purpose traffic. A multicentered bus rapid transit system would serve commute trips between suburban residential areas and major employment centers. The transit system would be supplemented with a flexible carpooling system. An enhanced version of the concept would introduce variable peak period tolls to encourage further mode shifts, reduce traffic demand, and help pay for system costs. Sketch planning estimates of costs for freeway, transit, and flexible carpooling investments suggested that the capital costs could be self-financed through road-pricing revenues.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.