1 to 10 F.; note that 15 percent of the hauling power is lost and
the corresponding weather factor is 85 percent, the percentage of
hauling power the locomotive retains when the temperature is in this
Table III. Effect of Weather Upon Hauling Power of Locomotives
Wet weather is usually regarded as local and temporary, and loss
of hauling power caused by it is absorbed by average figures.
Therefore, no reduction in hauling power is normally made for wet
weather. In some areas of the world, however, where there are
extended wet seasons such as monsoons and heavy fogs, a loss in
tractive effort due to slippery rails may be serious if adequate
sanding facilities are lacking. The amount of reduction that the
planner should use in these areas is a matter of judgment; but, in
general, he should not use a figure for it less than 20 percent of
the weight on drivers.
2.10. GROSS TRAILING LOAD
Once you have found the potential power in a locomotive and the
reasons that all of this power cannot be used to haul freight, the
next step in planning is to determine how much weight in railway cars
and freight can be attached behind and moved by a particular
locomotive. This weight is known as the gross trailing load (GTL).
Expressed in short tons, GTL is the maximum weight or load that a
locomotive can safely pull behind it over a given line in known
weather. It is determined by using the following formula which
combines the factors discussed in paragraphs 2.5 through 2.9.