This presentation is the property of its rightful owner.
1 / 9

# A mathematical modeling approach to improving locomotive utilization at a freight railroad PowerPoint PPT Presentation

A mathematical modeling approach to improving locomotive utilization at a freight railroad. Kuo and Nicholls. Introduction. Rail has lost business to other modes in the past but is recapturing lost business Fuel efficiency advantage Computerized scheduling and routing

A mathematical modeling approach to improving locomotive utilization at a freight railroad

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

## A mathematical modeling approach to improving locomotive utilization at a freight railroad

Kuo and Nicholls

### Introduction

• Rail has lost business to other modes in the past but is recapturing lost business

• Computerized scheduling and routing

• Upgrading of equipment, terminals, etc.

• Improved railcar identification system

• M&A for scale economies

• This paper discusses one approach which Conrail has taken to improve efficiency

Background

• Conrail (at the time of study)

• 11,700-mile rail network

• Over 2,000 engines

• Challenges

• Efficiently position train crews and engines

• 12-hour on-duty constraint

• Return home or lodging after 12 hours

• Geographic imbalances of locomotive availability due to variable traffic pattern

• “Light” engine moves are necessary

• Minimize light engine moves

Purpose

• Develop a math model to minimize cost of light engine moves

• Cost savings can be large because

• Engines value \$1.1 billion

• Current operation is based on expert judgment

• Difference from previous studies

• Schedule assumed to repeat on a 7-dat cycle (not 24 hours)

• Cost of light engine moves emphasized (not treated as sub-problem)

Model

• Minimize the cost of light engine move

• Fixed cost = labor cost, taxi cost, lodging cost, over-mileage cost

• Variable cost = fuel cost

• Decision variables

• Distribution of engines among yards at the start of each week

• Necessary light engine moves between yards

• Constraints

• Engine (horsepower) requirements

• No more than 15 light engine moves per day

• Other “common sense” conditions

Illustrative Application

• Data

• Three-yard data (from Conrail)

• Assumed closed system

• 16 available engines (minimum needed)

• 105 decision variables, 106 constraints

• Results

• Minimized cost = \$4,920.22

• Current method = \$6,233.97

• Saving of \$1,313.75 (about 21%)

• In reality, cost savings can be larger (more opportunities for savings)

Sensitivity Analysis

• Increased the available engines from 16 to 17

• Investigate if increasing the fleet size is better (trade off between fleet size and light move)

• Minimized cost = \$3,823.26 (saving of \$1,096.96)

• Equivalent to \$57,000 per year

• Worth increasing the fleet size?

• Acquisition cost of an engine = \$1.5 million

• Can be used for 30 years

• In reality the savings can be larger

Conclusion and limitation

• Cost saving potential

• Can learn from airline industry

• But be aware of limitations

• Engines are often exchanged among carriers

• Crews do not always stay at hotels (go home, “held-away-from-home” cost

• Train schedules change constantly over time

• Only the scheduled trains are considered

• One type of engine is assumed

• Maintenance downtime is ignored

Discussion questions

• What are implications of this study to railroads?

• Are railroads doing better job than airlines or motor carriers (in efficiency)?

• Is the proposed model usable in the field?

• What are pros and cons of railroads (as opposed to other mdoes)?

• What are the future of railroads? What should they do to increase the share of business?