AN ANALYSIS OF TRAFFIC OPERATION ON THE MARK TWAIN EXPRESSWAY AT I-270 IN ST LOUIS COUNTY

SEVERE CONGESTION HAS BEEN OBSERVED IN THE WEST BOUND LANES OF LTHE MARK TWAIN EXPRESSWAY IN THE VICINITY OF THE I-270 INTERCHANGE. THE OBJECTIVE WAS TO DETERMINE MORE PRECISELY THE EXTENT OF THIS CONGESTION WHILE SIMULTANEOUSLY DETERMINING THE FEASIBILITY OF IMPLEMENTING MEASURES TO IMPROVE OPERATION THROUGH THE AREA. FIELD DATA WERE COLLECTED USING TIME LAPSE AERIAL PHOTOGRAPHY, SUPPLEMENTED BY SPEED AND VOLUME MEASUREMENTS MADE ON THE GROUND. THE ORIGINAL STUDY PLAN WAS AIMED AT DETERMINING THE LENGTH OF ACCELERATION LANE NECESSARY TO ELIMINATE THE CONGESTION. THE ANALYSIS OF THE FILM HOWEVER, INDICATED THAT WHILE THE MERGING MOVEMENTS DID INDEED HAVE A PRONOUNCED EFFECT ON OPERATIONS, ESPECIALLY IN THE SHOULDER LANE, TRAFFIC ON THE RAMP WAS ABLE TO MERGE AS LONG AS TRAFFIC MOVED. THE AREA OF SUBSTANDARD OPERATIONS WS FOUND TO EXTEND DOWNSTREAM OF THE STUDY AREA. THE REASON FOR THE BREAKDOWN IN OPERATION WA DETERMINED AS EXCESS DEMAND. ANY IMPROVEMENT IN OPERATION AT THE MERGING POINTS UPSTREAM WOULD ONLY HAVE RESULTED IN AN INCREASE IN VOLUME REACHING THIS POINT, CAUSING WORSE CONGESTION THAN THAT WHICH ALREADY EXISTED. /FHWA/

• Record URL:
  https://spexternal.modot.mo.gov/sites/cm/CORDT/MCHRP70-9.pdf
• 
• Corporate Authors:

  Missouri State Highway Commission

  State Highway Building
  Jefferson City, MO  United States  65101

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Publication Date: 1971-12

Subject/Index Terms

• TRT Terms: Expressways; Highway operations; Merging traffic; Speed; Time lapse photography; Traffic; Traffic congestion; Traffic lanes; Traffic volume
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00224974
• Record Type: Publication
• Source Agency: Federal Highway Administration
• Files: TRIS, USDOT, STATEDOT
• Created Date: Jun 1 1971 12:00AM