Variable Speed Limit (VSL) - Best Management Practice

The Variable Speed Limit (VSL) system on the I-4 corridor in Orlando was implemented by Florida Department of Transportation in 2008, and since its deployment, it was revealed that the majority of traffic exceeds the speed limit by more mph when the speed limit is reduced versus when it is at the baseline level. The overall objective of this project was to gain a better understanding of the drivers’ perception of the I-4 VSL system, to evaluate operations along the VSL zone of the I-4, and to investigate VSL strategies that have the potential to improve operations along I-4. Focus group studies as well as in-vehicle observation studies were conducted to evaluate driver perceptions. Participants indicated they would typically not reduce their speeds unless the drivers/motorists in their surroundings reduce theirs, and they suggested installing the VSL sign boards on both the sides of the roadway and, if possible, on the overhead sign boards at each lane. Through a combination of sensor data analysis and aerial reconnaissance, the research team identified bottleneck locations and congestion times. Based on these, a CORSIM simulation of the I-4 VSL zone was built in order to evaluate various potential VSL algorithms and their respective settings. It was concluded that changing the detector configuration and using the data from the worst performing detector have the potential to increase speeds and to improve operations for some of the VSL scenarios tested. A VSL system along I-4 may be able to provide some limited operational improvement at specific bottlenecks and/or along the entire network. However, there is no clear pattern regarding the type of algorithm that would be most beneficial at a particular bottleneck, nor any clear patterns regarding the VSL sign configuration.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 199p

Subject/Index Terms

Filing Info

  • Accession Number: 01446922
  • Record Type: Publication
  • Contract Numbers: FDOT Contract BDK77 977-11 (UF Project 00088592)
  • Created Date: Sep 21 2012 9:38AM