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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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was quite small relative to the time during which the tow would typi-<br />

z.dly operate at its cruising speed. Also, it was found that the<br />

distance traveled by a tow during acceleration was small relative to<br />

typical trip distances. Likewise, deceleration was determined to be<br />

insignificant. The model predicting the cruising speed of the tow,<br />

then, is the major input to the process function as far as tow move-<br />

ment is concerned. That would be the end of things were it not <strong>for</strong><br />

the fact that tows are delayed en route. Delays occur because of,<br />

locking, assembly and disassembly of the tow, and other miscellaneous<br />

reasons. Locking delay was handled by a simple queuing model A<br />

delay relationship <strong>for</strong> making and breaking tow was estimated from .<br />

towboat log data. Finally, all other linehaul delays were grouped<br />

together and estimated from delay data collected by a common carrier<br />

barge firm.<br />

Given the above relationships, the ton-miles per hour generated<br />

by any given tow <strong>for</strong> any given trip may be estimated. .Moreover, the<br />

predicted ton-miles per hour figure is amenable to changes in vari-<br />

ables under the control of barging firms (e.g., horsepower of tow-<br />

boats) as well as variables under the control of the Corps of Engi-<br />

neers (e.g.., depth, width, and stream velocity of waterway; lock<br />

size). In addition, as will be shown in the next section, cost per<br />

ton-mile may be determined with the aid of the process function de-<br />

veloped above.<br />

Productivity relationships and isoquants will not be investi-<br />

gated <strong>for</strong> the tow process function. As was noted in Chapter II,<br />

Howe has investigated these relationships <strong>for</strong> his tow process<br />

115 ,

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