Doctoral Defense - Md Israt Khan

About the Event

The Department of Civil and Environmental Engineering

Michigan State University

Ph.D. Dissertation Defense

Monday, March 24, 2025 at 1:30 PM EDT

Engineering Building Room 2555D

Contact Department or Advisor for Zoom Information

ABSTRACT

UNDERSTANDING DRIVER BEHAVIOR IN NAVIGATING TURBO ROUNDABOUT

By: Md Israt Khan

Advisor: Dr. Kakan Dey

Turbo roundabouts minimize weaving conflicts by introducing raised lane separators within the circular lanes compared to conventional multi-lane roundabouts. Although widely used in Europe, turbo roundabouts are relatively new in the US. The California Department of Transportation installed a rotor turbo roundabout in San Benito County in 2024, which provided an opportunity to investigate US drivers’ behavior in navigating the turbo roundabout. This research aimed to analyze driver behavior and evaluate safety performance at this newly built turbo roundabout by performing descriptive analysis and statistical modeling. Results showed that approximately 5% of vehicles made prohibited lane changes within circular lanes, especially in performing left-turn movements. Lane-change model revealed that vehicle speed, vehicle type, and headway significantly influence lane-changing behavior. Speed choice model indicated that vehicle type, turning movement, radius of circular lane curvature, and time of day significantly affected vehicle speed on circular lanes. Observed critical gap values (4.38 to 5.79 seconds) were generally higher than conventional multi-lane roundabouts. Follow-up time was also higher (3.69 to 4.69 seconds) than conventional multi-lane roundabouts as drivers proceeded more cautiously due to raised lane dividers within circular lanes. Drivers on the turbo roundabout outer lane exhibited the shortest critical gaps than inner lanes, due to more complex merging events on inner lanes. Extreme Value Theory (EVT) analysis captured the relationship between conflict estimates and observed crashes. Based on average post-encroachment time (PET), extreme conflicts primarily caused by improper lane changes and failure to yield. Turbo roundabout significantly lowered crash severity and eliminated speeding-related crashes, where 83% of post-treatment/installation minor injury crashes were due to unfamiliarity and right-of-way violations. These findings underscore the need for improved dissemination of proper turbo roundabout driving information and appropriate signage to assist proper lane selection to avoid prohibited lane changes within circular lanes. This research contributes to broader understanding of turbo roundabout’s performance in the US, and findings can be used to refine design and capacity/operational/safety analysis based on driver behavior in the US.

Persons with disabilities have the right to request and receive reasonable accommodation. Please call the Department of Mechanical Engineering at 355-5131 at least one day prior to the seminar; requests received after this date will be met when possible.