lec10 - AN INTRODUCTION TO INTELLIGENT TRANSPORTATION...

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AN INTRODUCTION TO INTELLIGENT TRANSPORTATION SYSTEMS 1.212 SPRING 2005 Professor Joseph M. Sussman Mon/Wed 2:30-4:00 BLOCK 2 Lecture 10 ADVANCED TRAVELER INFORMATION SYSTEMS March 9, 2005 SPEAKER : Joseph M. Sussman MIT
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FREIGHT RELIABILITY DRIVEN BY INVENTORY AND STOCK-OUTS
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WHAT CAN GO WRONG? Delays along the way -- service reliability goods don’t arrive ISSUE: Stock-outs 80 40 1 2 3 Time Inventory at B
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WHAT CAN GO WRONG? (CONTINUED) So, perhaps the customer at B keeps a day’s worth of inventory Problems: Bigger Inventory Warehousing Costs Insurance Costs 80 1 2 3 4 Time (days) Inventory
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A BIG ISSUE -- STOCK- OUTS ± WHAT DOES A STOCK-OUT COST? ± Examples ± GM Assembly Plant ± Retail Store ± Blood Bank
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INVENTORY MINIMIZATION ± If one needs a greater amount of inventory because of unreliability in the transportation system or probabilistic use rate, you generate costs as a result of needing larger inventory to avoid stock-outs. ± We try to balance the costs of additional inventory with the costs of stock-outs.
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TOTAL LOGISTICS COSTS (TLC) Total Logistics Costs (TLC) = f (travel time distribution, inventory costs, stock-out costs, ordering costs, value of commodity, transportation rate, etc.)
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TRAVEL TIME DISTRIBUTION FROM SHIPPER TO RECEIVER t f(t) Figure 12.14 ± This probability density function defines how reliable a particular mode is. ± TLC is a function of the travel time distribution. ± As the average travel time and variance grows, larger inventories are needed.
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TRAVELER RELIABILITY NOW IT IS TIME UTILIZATION AND NOT INVENTORY WE ARE CONCERNED WITH
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± How can you deal with uncertainty in travel times? ± Choose time when conditions are stable ± Choose routes with stable conditions ± Choose routes you know ± Build knowledge through experiment ± Minimize consequences through safety margins ± Get better information before the trip or en route Bonsall, Peter, “Travellers’ Response to Uncertainty”, Chapter 1 in Reliability of Transport Networks , Bell and Cassir, eds., Research Studies Press Ltd., Baldock, Hertfordshire, England, 2000.
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80 min (50%), 60 min (50%) 70 min (100%) AB Risk Averse Bottom
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lec10 - AN INTRODUCTION TO INTELLIGENT TRANSPORTATION...

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