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See "A System Dynamics Model for Improving Railroad Performance" by Homer,
Keane et al. in ISDC 2000 CD-ROM. Also, "A System Dynamics Model for Long
Range Planning in a Railroad", by P Gottschalk in Eur J of Op Res (EJOR)
1983, 14(2).

-Jack Homer
From: JHomer609@cs.com

Folks, My reaction to the proposed reduction in the number of days that we would all be together at future conferences was similar to George Richardsons. The annual conference brings together for an extended period the constituencies that George mentioned, as well as another key constituency: studen...

Jim Hines is absolutely right to suggest that people too often add detail to models without good cause. It is certainly bad practice to pull new structure out of thin air in the misguided belief that improved curve fitting is its own justification. But we should recognize that improved understanding...

Geoff Coyle writes: >The simplifications are an important >consideration as there is otherwise a tendency to make the model more and >more and more detailed in a vain search for an illusion of accuracy. Yes, a basic tenet of modeling is to make the model only as detailed as necessary. The key phrase...

Geoff Coyle writes: > Im not sure about a non-linearity being more correct. As Jay once wrote > (like much in SD Forrester said it first and said it best) in a proper > model the decision functions correspond to those in the real system (quoted > from memory) and a non-linearity is a guesstimate as ...

Don Seville and Drew Jones ask an intriguing question: > When urban areas fill their land area, why do some tip towards decay and > others towards gentrified "wealthy enclaves"? As a grad student many years ago, I spent some time thinking about and modeling the issue of urban renewal. I be...