Week 13: Operations

Rail Traffic Control

  • Rail Signals and Traffic Control (Click to see Railroad definitions and more)
  • Rail is first (only?) mode where stopping distance > sight distance
  • Timetables first used, with 5 minutes red flares (fusees) thrown out by brakemen; still used in "dark" areas
  • Telegraph, later telephone and radio, allowed for train orders (define)
  • Rail is tightly controlled, compared to the highway
  • Direct train control provides the safest system, but signals can be and are used
  • In medium density situations, two-way radios are used to control trains
    Signals and Semiphores...
  • purpose is mostly for effiency (not safety)
  • red = stop/proceed slow = horizontal (in grade country, may have a permissive slow speed)
  • yellow = slow (approach) = 45 degrees
  • dark must be interpreted as most restrictive aspect
  • green = clear = vertical

    Block signaling ...

  • manual block - humans set signals, (in yards, with long pipes)
  • automatic block signaling (ABS) sets signals electronically with fail safe circuits
  • Sections of track called "blocks", circuit is shorted by presence of a train in a block (Click to see figure 5-8 from Ashford and Wright, and note the fail safe design, e.g., what happens if either battery fails?).
  • A battery keeps a relay open (and the signal clear) unless a train short circuits the battery, in this case, causing the signal to indicate stop (one block, two position).
  • Three aspect, two block systems provide better capacity. Why? In 2 block systems, the length of block is equal to stopping distance, only half that in 3 block - trains can slow to an intermediate speed
  • There must be NO CONFUSION over what a signal or a train order means

    Central traffic contol ...

  • Using coded impulses, CTC controls switches and signals at key points, providing higher capacity. Also allows in cab signals. Can provide 70% of capacity of double track on single track with sidings at much lower costs.
  • optical car recognition (a failure), replaced by transponder system
  • computer control and management, e.g., UP's Transportation Control System (TCS)
  • advanced train control (GPS) under development/study
  • CAD in railroading means "computer aided dispatch"
  • College Train Special: Click to see the Union Pacific control facility and more! (by Doug Jones, U of I)

    Links

    Terminals, Unit Trains, Intermodalism and Special Freight

    Switching

    • trailing point - back cars into siding
    • facing point - see figure 11-1
      - run around
      - flying switch (dangerous)
    Unit Trains
    • pre-staggers, no incentive to ship in bulk, why? contract rates were not allowed (to protect small shippers)
    • post-staggers ... unit trains
      - no switching
      - single waybill
      - fast load and unload
    Intermodal Operations
    • piggy back (TOFC/COFC) 23% of service now, why?
      bigger cars (2 trailers, 40s)
      deregulation
      container shipping (20s and 40s)
      double stack (53 or 40 on top of 40 or 2 20s) see fig. 15-4
    • loading
      ramp (circus) for small operations
      gantry or crane loading
      side loading (not standard)
    • TOFC more expensive to move, but less expensive to load/unload/switch than boxcars
    • COFC cheaper to move but need chasis
    • therefore, TOFC/COFC competes in markets > 500 miles.
    • road railers (high price goods)
    • COFC is 53% of intermodal and growing - with some containers not transporable by ship (48 and 53' containers)
    Links