Introduction to Transportation
Systems
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PART II:
FREIGHT
TRANSPORTATION
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Chapter 18:
Measuring Origin-Destination Service and Other Rail Issues
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Measuring OriginDestination Service
Trip Time Histogram
Schedule
2-day
%
P (N)
.5
.35
.1
.04
.01
2
3
4
5
6
N (in days)
Mean Trip Time N
Suppose we are using a “two-day” percent. Take a piece of
paper that is two days wide; you slide it back and forth along the
histogram until you find the pair of adjacent days that gives you
the largest probability, as in Figure 18.1. So a particular origindestination pair may have a two-day percent of 85%, which
means that the percentage of travel time in the best contiguous
two days, in this case three and four days, was 85%. In the
case of a high-quality intermodal service, the two-day percent
might well be 100%.
Figure 18.1
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Schedule Adherence
‹
‹
Schedule adherence is a measure that can be
easily manipulated. One can relax the
schedule and apparently perform better in the
sense that a larger number of cars are now on
schedule. But nothing has really changed.
This is a chronic problem in the airline
passenger industry. When the FAA publishes
data about schedule adherence, a notunreasonable response on the part of the
airlines is to change their schedules -- making
scheduled trip times longer. The operation
may not have changed at all. But performance
looks better on a schedule adherence basis,
because the schedule is easier to adhere to.
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Empty Freight Car
Distribution
Empty Moves
Origin of first load
Loaded move
Empty move
Destination
of first load
Origin of second load
Figure 18.2
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Competition and
Cooperation
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RR A
2
RR B
4
RR B
RR A
RR B
1
RRA and RRB cooperate on 2 - 4 traffic and compete on 1 - 2 traffic.
Figure 18.4
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Types of Mergers
RR A
RR A
Transfer
point
RR B
Parallel merger
RR B
End-to-end merger
RR A
RR B
RR A
RR B
RR B
Combined parallel/end-to-end merger
Figure 18.5
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General Merchandise
Service
Rail Network: Merchandise Service
Shipper
Local Train
A
Train AB
B
Train BC
Train EB
C
E
Local Train
Train BD
Receiver
D
F
Figure 18.6
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Types of Service
‹ Intermodal
Service
‹ Bulk Commodities
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Final Comments on Rail
‹
‹
Using different levels-of-service as a way of
managing capacity is an important transportation
concept, and is applicable to railroads.
There are many different kinds of capacities to be
allocated.
There is line-haul capacity; a track can
accommodate only so many trains a day; there is
terminal capacity, as one switches trains through
those facilities; capacity is also affected by the
number of freight cars in our inventory, the
amount of power on the system and labor and
management resources, among other items.
These are all ideas that are applicable to other
nodes.
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