AN INVESTIGATION OF FACTORS AFFECTING THE DESIGN LOCATION OF FREEWAY RAMPS

EXISTING FREEWAY INTERCHANGES HAVE BEEN DESIGNED USING THE CURRENT BEST DESIGN FOR EACH OF THE RAMPS, BUT THE LOCATION AND CONFIGURATION OF THE RAMPS HAVE FOR THE MOST PART BEEN ACCOMPLISHED IN A STANDARDIZED MANNER. THIS RESEARCH INVESTIGATED THE OPERATION OF SEVERAL EXISTING LAYOUTS AND THE SUITABILITY OF DIFFERENT LAYOUTS USED AT THESE LOCATIONS. TO DESIGN INTERCHANGES PROPERLY, THE RAMPS MUST BE LOCATED IN SUCH A MANNER AS TO FULFILL THE ESTIMATED FUTURE NEEDS OF TRAFFIC AND PROVIDE A MINIMUM OF INTERFERENCE TO THE FREEWAY TRAFFIC. THE STACKED RAMP CONFIGURATION WAS INVESTIGATED AS A POSSIBLE SOLUTION WHEN BOTH AN ON-RAMP AND AN OFF-RAMP WERE REQUIRED AT THE SAME LOCATION. RAMP LOCATION WAS DEFINED AS THE LOCATION OF A RAMP OF RAMPS UPSTREAM OF DOWNSTREAM OF AN ARTERIAL STREET CROSSING THE FREEWAY. THE DESIRED MOVEMENT OF ENTERING AND EXITING TRAFFIC AT DIAMOND OR X-TYPE INTERCHANGES WAS INVESTIGATED AS WELL AS THE FREEWAY RAMP CONFIGURATION ON THE AMOUNT OF ACCEPTABLE GAP TIME IN ORDER TO DETERMINE THE MOST DESIRABLE RAMP CONFIGURATION. THE STUDY PROCEDURE WAS A TEST OF THE HYPOTHESIS THAT THE GREATEST AMOUNT OF ACCEPTABLE GAP TIME AVAILABLE TO VEHICLES DESIRING TO ENTER THE FREEWAY WAS FURNISHED BY REMOVING OFF-RAMP TRAFFIC BEFORE ALLOWING ON-RAMP TRAFFIC TO ENTER. THE HIGH COST, THE LACK OF POTENTIAL FOR STAGE CONSTRUCTION, AND THE ADDITIONAL RIGHT-OF-WAY REQUIRED, INDICATE THAT THE CONSTRUCTION OF STACKED RAMPS MAY NOT BE GENERALLY FEASIBLE TO GAIN THE ADVANTAGE OF NO WEAVING ON THE FRONTAGE ROAD AND LESS DISTANCE REQUIRED ALONG THE FREEWAY TO FIT IN THE DESIGN. MINIMUM INTERCHANGE SPACING WAS PROVIDED BY THE TYPE I FREEWAY LAYOUT WHICH CONSISTED OF THE COMBINATION OF 2 INTERCHANGE LAYOUTS WITH AN OFF-RAMP LOCATED UPSTREAM OF AN ON-RAMP BOTH BEFORE AND AFTER AN ARTERIAL STREET.

Media Info

  • Media Type: Print
  • Features: Appendices; Figures; References; Tables;
  • Pagination: pp 1-35
  • Monograph Title: Geometric design, barrier rails and sign supports
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00203241
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Apr 6 1994 12:00AM