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Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

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eached <strong>for</strong> acceleration, which takes longer than deceleration, ,<br />

should apply a <strong>for</strong>tiori.<br />

Of the myriad delays encountered by tows, locking and tow as-<br />

sembly and disassembly account <strong>for</strong> the major portion of delay time.<br />

A simple queuing model is developed <strong>for</strong> predicting locking delay.<br />

The locking model estimates the amount of time a tow can expect to<br />

spend in the process of locking on any given trip. The model is<br />

sensitive to the number of tows operating on the waterway (which is<br />

estimated from total tonnage to be transported on the waterway, aver-<br />

age tow size, and an empty backhaul factor) and to the characteris-<br />

tics of the locks themselves. The model is checked against actual<br />

average locking times and found to predict well.<br />

The time involved in assembly and disassembly of tows is found<br />

to be accurately estimated by linear relationships in which the num-<br />

ber of barges comprising the tow is the independent variable. That<br />

is, making and breaking tow each requires a constant amount of time<br />

irrespective of the number of barges in the tow and an amount of<br />

time proportionate to the number of barges in the tow.<br />

All other delay time (e.g., that due to weather, running<br />

aground, etc,) is classified as miscellaneous. The time consumed<br />

by miscellaneous.delays is found to be proportionate to tow running<br />

time, the factor of proportionality being estimated as 14 percent.<br />

• That is, a trip which would require 10 hours with no delaya could be<br />

expected to encounter miscellaneous delays amounting to 1.4 hours.<br />

Given these delay analyses, the tow linehaul process function<br />

is complete and may be used to estimate productivity and cost<br />

186

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