VEHICLE COMMUNICATIONS FOR DIAL-A-RIDE SYSTEM

"CARS" IS A DOOR-TO-DOOR TRANSPORTATION SYSTEM USING DYNAMICALLY ROUTED 10-20 PASSENGER VEHICLES. A TELEPHONED REQUEST FOR SERVICE WILL BE FED INTO A COMPUTER WHICH WILL EXAMINE CURRENT VEHICLE LOCATIONS AND ASSIGNMENTS AND INSERT THE NEW REQUEST INTO THE TENTATIVE TOUR OF THE MOST APPROPRIATE VEHICLE. TO ACHIEVE THE DYNAMIC ROUTING WHICH IS ESSENTIAL, AND TO ALLOW FOR POSSIBLE REASSIGNMENTS AS THE DEMAND SITUATION DEVELOPS, EACH VEHICLE WILL RECEIVE INFORMATION AS TO ITS NEXT DESTINATION ONLY ONE STOP AHEAD. THIS INFORMATION MUST OBVIOUSLY BE TRANSFERRED WITH MINIMUM DELAY, SINCE THE VEHICLE CANNOT PROCEED UNTIL IT HAS ITS NEW DESTINATION. THE ANTICIPATED SERVICE LEVELS IN EVENTUAL CARS SYSTEMS RANGE FROM 500--2000 DEMANDS (PASSENGER SERVICE REQUESTS) PER HOUR. THIS WILL REQUIRE 1000--4000 RADIO DISPATCH MESSAGES PER HOUR, AS A SINGLE DEMAND WILL USUALLY RESULT IN TWO DISPATCH MESSAGES---ONE FOR PICKUP AND ONE FOR DELIVERY. SINCE THIS LEVEL OF DISPATCH ACTIVITY IS CONSIDERABLY IN EXCESS OF CURRENT PRACTICE IN ANALOGOUS APPLICATIONS, SUCH AS TAXI DISPATCHING, AN IMPORTANT PART OF THE "CARS" SYSTEMS STUDIES IS VEHICLE COMMUNICATIONS. DIGITAL TRANSMISSION SYSTEMS ARE RECOMMENDED THAT OPERATE AT 1000 BITS PER SECOND ON A SINGLE CHANNEL PAIR WHICH COULD TRANSMIT 3600 40-CHARACTER MESSAGES PER HOUR, SUFFICIENT TO DIRECT 180 VEHICLES AND SIMULTANEOUSLY POLL THE VEHICLE FLEET AT A RATE OF 40 VEHICLES PER SECOND FOR DRIVER INPUTS OR RESPONSES. SINCE ALL MESSAGE TRAFFIC WOULD BE DIGITAL, THE SCHEDULING COMPUTER AND COMMUNICATIONS SYSTEM WOULD BE DIRECTLY CONNECTED, AND ONLY A SUPERVISORY OR EMERGENCY VOICE DISPATCHING CAPABILITY NEED BE RETAINED. COST COMPARISONS FOR VOICE AND DIGITAL COMMUNICATIONS SYSTEMS INDICATE THAT FOR A 30-VEHICLE SYSTEM WITH ALL COMMUNICATIONS EQUIPMENT COSTS AMORTIZED OVER TWO YEARS OF OPERATION, THE GREATER INITIAL EQUIPMENT COST OF A DIGITAL SYSTEM WOULD JUST BALANCE THE ADDED LABOR COSTS IN A VOICE SYSTEM. THE VOICE SYSTEM WOULD BE MORE EXPENSIVE FOR EITHER LARGER CARS SYSTEMS OR FOR LONGER PERIODS OF OPERATION, AND WOULD REQUIRE MORE RADIO CHANNELS. THE COMPUTER--VEHICLE LINK WOULD BE PROVIDED BY A CHARACTER-ORIENTED DIGITAL COMMUNICATIONS SYSTEM. THE SYSTEM INCLUDES A SMALL GENERAL- PURPOSE COMPUTER, PERIPHERAL TO THE SCHEDULING COMPUTER, TO HANDLE ALL THE TASKS ASSOCIATED WITH COMMUNICATIONS. /UMTA/

  • Supplemental Notes:
    • PROJ NO MASS-MTD-6
  • Corporate Authors:

    Massachusetts Institute of Technology

    Urban Systems Laboratory, 77 Massachusetts Avenue
    Cambridge, MA  USA  02139
  • Publication Date: 1971-3

Subject/Index Terms

Filing Info

  • Accession Number: 00242047
  • Record Type: Publication
  • Source Agency: Urban Mass Transportation Administration
  • Files: TRIS, USDOT
  • Created Date: Oct 15 1972 12:00AM