Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Civil, Construction, and Environmental Engineering


Civil Engineering

First Advisor

Anuj Sharma


Traffic speed control devices have an important role in transportation systems. Static devices, such as speed limit signs, can advocate safe and efficient traffic movements by displaying appropriate speed limits. Changeable message signs have many applications in adjusting the dynamic nature of a transportation system. These applications include but are not limited to variable speed limits based on ambient traffic conditions, work zone management, and warnings about severe weather conditions.

This dissertation evaluated the performance of multiple traffic speed control devices, including static speed limit signs and dynamic changeable message signs. By identifying existing problems, such as data smoothing, traffic characteristics clustering, and event classification, the author proposed some practical engineering solutions for better performance. One of the highlighted applications is a text alert system that actively monitors 50 Iowa work zones, which are equipped with more than 350 roadway sensors, and sends multimedia alert texts to district traffic engineers. The application of a variable advisory speed limit system that reports severe winter weather conditions was also implemented/validated and currently runs in “ghost” mode (without displaying any visible messages to the public) until it is approved.

After conducting a series of analyses in the transportation macroscopic world (data collected by roadway traffic sensors), the current dissertation research expanded into the microscopic driver speed behavior analysis (data collected by instrumented vehicle sensors). A naturalistic driving study focusing on older drivers collected a large amount of detailed individual driving data from multiple sources with high resolutions, including timestamped speed, acceleration, deceleration, and geo locations. This abundant dataset enabled the author to examine an individual’s driving behavior with respect to different speed limits and other factors.

Copyright Owner

Shefang Wang



File Format


File Size

87 pages