Introduction of Cooperative Vehicle-To-Infrastructure Systems to Improve Speed Harmonization

Chapter 3. Conclusions

This project implemented speed harmonization algorithms on an active freeway with recurring spatially structured congestion in simulation and field testing using a fleet of CAVs. Due to resource constraints, the field experiments could only deploy a maximum of three CAVs. Simulation results across three platforms (VISSIM^®, INTEGRATION^©, and Aimsun^®) showed that the introduction of three CAVs, with a goal of harmonizing overall speeds, would not be beneficial on a real-world freeway.

The simulation results indicated that a field experiment with a limited volume of CAVs was unlikely to cause a significant negative impact on traffic. The field experiment demonstrated that CAVs, with automation in the form of modifications to the OEM-supplied ACC, can be used in automated longitudinal control mode to implement V2I-based speed harmonization. The impacts on the traffic stream were measured using probe vehicles leading and following the CAVs. Furthermore, this project demonstrated that traffic stream trajectories after speed harmonization reduced oscillatory behavior as characterized using the power spectral densities of the measurements. In addition, there was no disbenefit in terms of travel times between the probe vehicles before and after speed harmonization.