Improving Energy Efficiency of Intermodal Trains Using Machine Vision and OR Analyses

Yung-Cheng LaiChris BarkanUniversity of Illinois at Urbana - Champaign

August, 2007

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Intermodal traffic had increased 77% since 1990

Containers(193% increase)

Total(77% increase)

Trailers(15% decrease)

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57.0 55.5

87.5 85.573.3

89.3

107.0

151.4

98 99 00 01 02 03 04 05

As of 2005, fuel costs had increase by nearly 3 folds since 1999

Average Cost Per Gallon(Cents)

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Intermodal (IM) trains incur greater aerodynamic penalties and fuel consumption than general trains

IM trains suffer from their equipment design and loading pattern

These large gaps directly affect the aerodynamic drag of the train. This effect is greater at higher speed

It is thus ironic that IM trains are the fastest freight trains operated in North America

Consequently, we undertook an investigation of options to improve IM train loading and fuel efficiency

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Loads should be assigned not only based on “slot utilization” but also “slot efficiency”Slot utilization: a metric used to measure the percentage of the spaces (a.k.a. slots) on intermodal cars that are used for loads

Maximizing slot utilization improves train energy efficiency because it eliminates empty slots and the consequent large gaps

However, it does not account for the size of the space compared to the size of the load

Two trains may have identical slot utilization, but different loading patterns and aerodynamic resistance

Slot efficiency: loads are matched with cars so as to minimize gaps

By using slot efficiency, train resistance could be lowered by as much as 27% and fuel savings by as much as 1 gal/mile/train (= 2.37 liter/km/train)

100 %

100 %

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A machine vision system has been developed to monitor the slot efficiency of intermodal trains

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Automated Monitoring System at Logistic Park Chicago (LPC)

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The system first captures video of the train and then process it to evaluate loading efficiency

Train Panorama Reconstruction From Input Video with Identified Gaps and

Detection of Containers/Trailers

Train Video

TrainMonitoring

ModuleGap

Document

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GapDocument

HistogramModule

Histogram of Upper Gap

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Histogram of Lower Gap

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Frequency diagram is used to evaluate the aerodynamic efficiency of IM trains

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Slot efficiency represents the loading efficiency by comparing the difference between the actual and ideal loading configuration

Every slot in each type of railcar has an ideal load that can be determined by using the loading capability of each railcar acquired from Universal Machine Language Equipment Register (UMLER)

Slot efficiency is similar to slot utilization except that it also factors in the energy efficiency of the load-slot combination

100%Length of actual loadLength of ideal load

Using “Slot Efficiency” to examine the loading efficiency of IM trains

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A model to automatically assign loads to the train ensuring minimum fuel consumption is needed

At IM terminals, terminal managers often use computer software as decision making tools to comply with loading assignment rules

However, loading assignment is still a largely manual process

Because cars in an IM train generally are not switched, managers primarily control the assignment of loads but not the configuration of the cars in a train

The current goal of loading is to reach the highest possible slot utilization

Although perfect slot utilization indicates maximal use of spaces available, it does not ensure that IM cars are loaded to maximize the energy efficiency

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“Gap Length” and “Position in Train” are the two most important factors to IM train aerodynamics

Based on the wind tunnel testing of rail equipment, three important factors to IM train aerodynamics were identified:

1. Gap Length between the IM loads2. Position in Train3. Yaw Angle: wind direction

(canceled out over the whole route)

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Unit (k) Drag area (CDA) Adjusted factor# (ft2)

1 (locomotive) 31.618 1.54492 28.801 1.40733 26.700 1.30464 25.133 1.22805 23.963 1.17096 23.091 1.12837 22.440 1.09648 21.954 1.07279 21.591 1.055010 21.320 1.0418100 20.466 1.0000

The front of the train experiences the greatest aerodynamic resistance

Objective:Minimize the total “adjusted” gap length within the train(adjusted gap length = adjusted factor x actual gap length)

base value

Placing loads with shorter gaps in the frontal position generates less aerodynamic resistance

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Minimize the total “adjusted” gap length within the train

Where:i = Type of the Load (40’, 48’, 53’ etc.)j = Load Number within the Specific Typep = Position in the Unit (P1 or P2)k = Unit Number (1,2,…,N)Ak = Adjusted Factor of kth GapUk = Length of kth UnitLi = Length of ith Type Load (ft)yijpk = 1 if jth Load in i Type was Assigned to kth Unit pth Position; 0 otherwise

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1 11 1 1 1 12 2

N

kk

ij i k ij k i k ij k ii j i j i j

AA U y L U y L U y LMinimize

U1 U2

1i ij ki j

L y 1 1i ij ki j

L y

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Loading assignment must follow loading capability of each unit as well as length & weight constraints

Subject to:

Where:Ripk = Loading Capabilitywij = Weight of jth Load in i TypeCk = Weight Limit of kth UnitQkp = Length Limit of Position p in kth Unit

k = 1 for Well-car Unit; 0 Otherwise= A Large Positive Number

xk = 1 if the top slot of kth Unit can be used; 0 otherwise

2 k

1 k

1 ,

40 (1 ) (such that 1)

(such that 1)

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ijpk ipkp k

ij k i ki j

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y x

loading capabilities

double-stack rules

weight constraint

length constraint

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A train can be more efficiently operated if loads are assigned based on slot efficiencyThe developed machine vision system monitors the loading patterns of IM trains and provides feedback to the terminal

By using the automatic loading assignment model, the potential fuel savings can be as much as 0.95 gal/mile/train (= 2.25 liter/km/train)

Extrapolating the savings over the BNSF Chicago-LA route (2,200 miles) would be at least 1,500 gal/train (= 5,678 liter/train)

The loading assignment model can be integrated into terminal operation software to help managers make the best decisions

Thank You