safe limiting speed, particularly for the
express service, is necessarily considerably less than it would be on
straight tracks.

The average speed of express trains between City Hall and 145th Street
on the West Side will approximate 25 miles an hour, including stops.
The maximum speed of trains will be 45 miles per hour. The average
speed of local and express trains will exceed the speed made by the
trains on any elevated railroad.

To attain these speeds without exceeding maximum safe limiting speeds
between stops, the equipment provided will accelerate trains carrying
maximum load at a rate of 1.25 miles per hour per second in starting
from stations on level track. To obtain the same acceleration by
locomotives, a draw-bar pull of 44,000 pounds would be necessary--a
pull equivalent to the maximum effect of six steam locomotives such as
were used recently upon the Manhattan Elevated Railway in New York,
and equivalent to the pull which can be exerted by two passenger
locomotives of the latest Pennsylvania Railroad type. Two of these
latter would weigh about 250 net tons. By the use of the multiple unit
system of electrical control, equivalent results in respect to rate of
acceleration and speed are attained, the total addition to train
weight aggregating but 55 net tons.

If the locomotive principle of train operation were adopted,
therefore, it is obvious that it would be necessary to employ a lower
rate of acceleration for express trains. This could be attained
without very material sacrifice of average speed, since the average
distance between express stations is nearly two miles. In the case of
local trains, however, which average nearly three stops per mile, no
considerable reduction in the acceleration is possible without a
material reduction in average speed. The weight of a local train
exceeds the weight of five trail cars, similarly loaded, by 33 net
tons, and equivalent adhesion and acceleration would require
locomotives having not less than 80 net tons effective upon drivers.

[Sidenote: _Switching_]

The multiple unit system adopted possesses material advantages over a
locomotive system in respect to switching at terminals. Some of the
express trains in rush hours will comprise eight cars, but at certain
times during the day and night when the number of people requiring
transportation is less than during the morning and evening, and were
locomotives used an enormous amount of switching, coupling an