• Skip to primary navigation
  • Skip to main content
Logo

Work Zone Safety Information Clearinghouse

Library of Resources to Improve Roadway Work Zone Safety for All Roadway Users

  • About
  • Join Listserv
  • Contact
  • Twitter
  • Facebook
  • LinkedIn
  • Work Zone Data
    • At a Glance
    • National & State Traffic Data
    • Work Zone Traffic Crash Trends and Statistics
    • Worker Fatalities and Injuries at Road Construction Sites
  • Topics of Interest
    • Commercial Motor Vehicle Safety
    • Smart Work Zones
    • Transportation Management Plans
    • Accommodating Pedestrians
    • Worker Safety and Welfare
    • Project Coordination in Work Zones
  • Training
    • Flagger
    • Online Courses
    • Toolboxes
    • FHWA Safety Grant Products
    • Certification and
      Accreditation
  • Work Zone Devices
  • Laws, Standards & Policies
    • COVID-19 Guidance
  • Public Awareness
  • Events
  • About
  • Listserv
  • Contact
  • Search
Publication

Construction Area Late Merge (CALM) System

Abstract:

The system evaluated comprised 5 VMS, 4 RTMS, 2 microwave traffic sensors, and a laptop-based system control center, all integrated via UHF radio system. The system monitors traffic at each VMS and dynamically changes the messages displayed on the VMS and the operational mode of the system based on traffic conditions downstream of each respective VMS. Three operational modes were defined: early merge, late merge, and incident. Modes were characterized by traffic speeds. Threshold speeds where the system transitioned from one mode to another were based on prior research combined with site characteristics. The test site was an approach to a freeway to freeway interchange reconstruction in Kansas City. When the system was in late merge operation, lane distributions were statistically different than when in early merge operation, but the difference was small. An entrance ramp near the merge appeared to have a very strong effect on driver lane choice, influencing drivers to merge left, even when the system instructed them to hold their lanes. The system performed well (i.e., with few technical difficulties). The results underscored the importance of considering site characteristics very carefully when selecting sites for deployment of dynamic systems and/or late merge systems, and when designing the system deployment configuration.

Publisher: Iowa State University
Publication Date: 2004
Full Text URL: Link to URL
Publication Types: Books, Reports, Papers, and Research Articles
Topics: Changeable Message Signs; Dynamic Lane Merge Systems; Evaluation and Assessment; Intelligent Transportation Systems; Merging Control

Copyright © 2023 American Road & Transportation Builders Association (ARTBA). The National Work Zone Safety Information Clearinghouse is a project of the ARTBA Transportation Development Foundation. It is operated in cooperation with the U.S. Federal Highway Administration and Texas A&M Transportation Institute. | Copyright Statement · Privacy Policy · Disclaimer
American Road and Transportation Builders Association Transportation Development Foundation, American Road and Transportation Builders Association U.S. Department of Transportation Federal Highway Administration Texas A&M Transportation Institute