Authors: Nan Zou and Jianwei Wang
Conference: Application of Advanced Technology in Transportation (AATT), Chicago, IL
Date: August 13-16, 2006
Abstract:
This paper presents a video-based method for evaluating and validating volume and speed data collected with traffic detectors. Assessing the detector data reliability is a critical task for all Intelligent Transportation Systems (ITS). Their performance will be significantly impacted by the data quality. Most existing studies mainly use volume as the only variable for evaluating the detector quality. A cost-efficient and rigorous method that can concurrently evaluate both volume and speed from the detectors is not available yet. The video-based method presented in this study is both cost-efficient and sufficiently reliable for evaluating detector data for ITS system operations. For example, the performance of a travel time prediction system is very sensitive to the quality of the detector data. This paper will mainly detail the key features of the proposed system and its application in a case study of RTMS detector data on I-70 corridor in Maryland.

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Authors: Xianfeng Yang, Gang-Len Chang, Saed Rahwanji
Conference: 92th TRB Annual Meeting in 2013
Unconventional Design: DDI
Purpose:

• Developed a set of planning models for DDI geometry design based on the estimated maximal queue length for each link.
• Developed a signal optimization plan for DDI to achieve signal progressions.

Abstract:
As one of the most popular unconventional interchange designs, diverging diamond intersection (DDI) has received increasing attention over the past decade. This study, responding to the needs, has produced a reliable and convenient system for traffic engineers to perform operational analysis of DDI. The entire system comprises three modules for planning analysis, signal optimization, and operational evaluation. At the planning stage, this system presents a set of empirical equations for engineers to compute the overall interchange delay and identify the potential queue spillback locations in a DDI design. The second module aims to provide the optimal signal plans to prevent the potential queue blockage. This module is unique in its consideration of the interdependent relations between queues at a DDI’s closely-spaced intersections, and the impacts by both geometrical constraints and traffic volumes. Given the traffic volumes, geometrical features, and signal timings, the system’s third module provides users to link a VISSIM-based simulation model to estimate the resulting traffic queues and interchange delays. Numerical analysis with four real-world DDI designs has revealed the effectiveness of the proposed system.

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