A research team at UT Austin developed tools to evaluate Active Traffic Management strategies for freeway corridors, providing useful details on the strengths and weaknesses of various approaches.
A Planning Tool for Active Traffic Management Combining Microsimulation and Dynamic Traffic Assignment
Research from the Center for Transportation research at the University of Texas at Austin focused on developing tools for evaluating the effectiveness of Active Traffic Management (ATM) strategies for freeway corridors. The research team performed a detailed microsimulation analysis for four ATM strategies under cases of recurring and non-recurring congestion. Ramp metering, variable speed limits, and hard shoulder running are found effective on the Williamson County test network on the outskirts of Austin, Texas.
In this study, the team chose to use the VISSIM micro-simulator developed by PTV. Performance of traffic flow on a freeway corridor was measured with the following metrics:
- Travel time
- Travel time reliability
- Traffic speed
- Queuing delay
To measure these metrics from simulation, the research team used the built-in evaluation functions in VISSIM. To perform microsimulation analysis of the ATM strategies, the Williamson County testbed was used. The team selected a segment of I-35 SB for implementing ATM strategies. Frontage roads parallel to the I-35 corridor were also included. The total length of this corridor is 3.7 miles. The perpendicular arterials were also included at the three interchanges.
- For the recurring congestion scenario, ramp metering, variable speed limits, and hard shoulder running were found to improve the corridor travel time and network performance for the selected test-bed. Certain control algorithms and their parameters were found to show an improvement of 5 to 16 percent in the system delay. The percent change for dynamic lane-use control near ramp merge and freeway-arterial coordinated operations was found insignificant.
- Ramp metering and variable speed limit led to a reduction in corridor travel time when combined, in comparison to the isolated use of each individual strategy. However, the overall network performance decreased when the strategies were used in combination.
- For the non-recurring congestion scenario, all strategies led to a worse network performance as compared to the case without the strategy—except for variable speed limits, which showed a 27.2 percent reduction in system delay and freeway-arterial coordinated operations, creating a 15 percent reduction in system delay.