Freeway Performance Measurement in a Connected Vehicle Environment Utilizing Traffic Disturbance Metrics

Authors

Leila Azizi, Florida International UniveristyFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Civil Engineering

First Advisor's Name

Mohammed Hadi

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Albert Gan

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Xia Jin

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

B.M. Golam Kibria

Fourth Advisor's Committee Title

Committee Member

Keywords

Microscopic Measures, Traffic Disturbance, Surrogate Measures, Platooning, Traffic State Categorization, Traffic Flow Breakdown, Safety Measures, Clustering Analysis, Machine Learning, Connected Vehicle Data

Date of Defense

11-15-2019

Abstract

The introduction of connected vehicles, connected and automated vehicles, and advanced infrastructure sensors will allow the collection of microscopic measures that can be used in combination with macroscopic measures for better estimation of traffic safety and mobility. This dissertation examines the use of microscopic measures in combination with the usually used macroscopic measures for traffic congestion evaluation, traffic state categorization, traffic flow breakdown prediction, and estimation of traffic safety. The considered macroscopic measures are the mean speed, traffic flow rate, and occupancy. The investigated microscopic measures for the stated purpose are: standard deviations of individual vehicle’s speeds, standard deviation of vehicles’ speed, and disturbance metrics. The utilized disturbance metrics to capture the stop-and-go operations are: the number of oscillations and a measure of disturbance durations in terms of the time exposed time–to–collision (TET), which has been used in other studies as a safety surrogate measure. However, this measure of disturbance duration requires the location and speed of both the leading and following vehicles and therefore cannot be measured accurately with low sample sizes of connected vehicles (CV). Thus, this study derived a model to estimate this measure based on speed parameters. The developed model was tested using real-world trajectory data from two locations that were not used in the development of the model.

Moreover, the percentage of vehicles in the platoon and the platoon size distribution were evaluated as additional indicators of congestion. The relationship between the platooning and disturbance metrics and the speed parameters were further explored. It is recognized that the parameters required to identify the platoons, such as the time headway, will not be available based on data from low market penetrations of CV. Thus, a model was developed that utilize other measures for the estimation of the platooning measures at lower CV market penetrations.

For the purpose of traffic state recognition and prediction, first, the study used a hybrid of two unsupervised clustering techniques to classify traffic states into “breakdown” and “non-breakdown”. The study found that adding the disturbance metrics in data clustering when identifying the traffic states will result in better traffic state recognition and traffic flow breakdown identification by capturing the disturbances in the traffic stream. The categorized traffic state was then used as a binary response to the macroscopic and microscopic measures, as features, to train supervised machine learning techniques for predicting traffic flow breakdown in the following 5-minute interval in real-time operations. The study found that utilizing disturbance and safety surrogate metrics in the real-time classification of traffic flow state increases the accuracy of prediction.

Also, the study showed that the investigated disturbance metrics and associated models and thresholds are significantly related to crash frequencies and thus can be used in the activation of transportation management strategies to reduce the probability of unsafe traffic and ease traffic disturbances that have adverse impact on traffic safety.

Identifier

FIDC008844

ORCID

https://orcid.org/0000-0001-8655-0027

Recommended Citation

Azizi, Leila, "Freeway Performance Measurement in a Connected Vehicle Environment Utilizing Traffic Disturbance Metrics" (2019). FIU Electronic Theses and Dissertations. 4319.
https://digitalcommons.fiu.edu/etd/4319