A METHOD OF TRAFFIC ASSIGNMENT TO AN URBAN NETWORK

THE SYSTEM DEVISED FOR TRAFFIC ALLOCATION PLANNING IN PROVIDING NEW NETWORKS OF FACILITIES FOR FUTURE TRAVELERS IN CHICAGO IS PRESENTED. A MODIFICATION WAS MADE OF THE MINIMUM PATH PROGRAM TO BRING THE TRAFFIC ASSIGNMENT WITHIN THE RANGE OF COMPUTATIONAL FEASIBILITY. THE METHOD DEVELOPED RAPIDLY ASSIGNS TRAVELERS TO THE SURFACE ARTERIAL STREETS AS WELL AS TO EXPRESS ROUTES AND TO RAPID TRANSIT AND SURFACE TRANSIT ROUTES. THIS CAPABILITY WAS A NECESSITY BECAUSE OF THE SHEAR MAGNITUDE OF THE CHICAGO TRANSPORTATION TRAFFIC ASSIGNMENT PROBLEM. THE STREET NETWORK WAS REPRESENTED TO THE COMPUTER BY IDENTIFYING THE FOLLOWING KEY PROPERTIES OF THE NETWORK: (1) THE NETWORK OF STREETS AND HIGHWAYS CONSIST OF INTERSECTIONS AND ROUTE SECTIONS BETWEEN INTERSECTIONS, (2) THIS NETWORK CAN BE MAPPED SO THAT EACH INTERSECTION IS PLACED AT A POINT IN AN OBLONG MATRIX OF POINTS MEASURING 55 X 95. THIS PERMITS A MAXIMUM OF 5,225 INTERSECTIONS. DIAGRAMS ARE PRESENTED OUTLINING THIS METHOD. ORIGIN-DESTINATION DATA WERE COLLECTED TO COORDINATE WITH THE SIMULATION OF TRAFFIC FLOW. THE MACHINE PROGRAM COMPUTES THE JOURNEY TIMES FROM A SINGLE ZONE TO EVERY OTHER ONE. THEREFORE, THE ELAPSED TRAVEL TIMES BETWEEN THAT ZONE AND THE OTHERS ARE AVAILABLE IN THE COMPUTER MEMORY. CHANGES IN THE NETWORK OF STREETS TO BE USED CAN BE CALCULATED IN A NEW TRAVEL INTERCHANGE. IT IS CONCLUDED THAT ANY TRAFFIC ASSIGNMENT TO A SINGLE ROUTE WOULD BEST BE MADE IF THE ENTIRE NETWORK WERE TREATED AND THERE WERE SOME ADJUSTMENT IN ZONAL INTERCHANGE VOLUMES.

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Filing Info

  • Accession Number: 00241087
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 16 1994 12:00AM