1/4"
Axles, diameter at center,.................. 6-1/2" 4-3/4"
Axles, diameter at gear seat,............... 7-13/16"
Axles, diameter at wheel seat,.............. 7-3/4" 5-3/4"
Journals,................................... 5" x 9" 4-1/4" x 8"
Journal boxes, malleable iron,
M. C. B. Standard,....................................

Both the motor and the trailer trucks have been designed with the
greatest care for severe service, and their details are the outcome of
years of practical experience.

CHAPTER IX

SIGNAL SYSTEM

Early in the development of the plans for the subway system in New
York City, it was foreseen that the efficiency of operation of a road
with so heavy a traffic as is being provided for would depend largely
upon the completeness of the block signaling and interlocking systems
adopted for spacing and directing trains. On account of the importance
of this consideration, not only for safety of passengers, but also for
conducting operation under exacting schedules, it was decided to
install the most complete and effective signaling system procurable.
The problem involved the prime consideration of:

Safety and reliability.

Greatest capacity of the lines consistent with the above.

Facility of operation under necessarily restricted yard and
track conditions.

In order to obtain the above desiderata it was decided to install a
complete automatic block signal system for the high-speed routes,
block protection for all obscure points on the low-speed routes, and
to operate all switches both for line movements and in yards by power
from central points. This necessarily involved the interconnection of
the block and switch movements at many locations and made the adoption
of the most flexible and compact appliances essential.

Of the various signal systems in use it was found that the one
promising entirely satisfactory results was the electro-pneumatic
block and interlocking system, by which power in any quantity could be
readily conducted in small pipes any distance and utilized in compact
apparatus in the most restricted spaces. The movements could be made
with the greatest promptness and certainty and interconnected for the
most complicated situations for safety. Moreover, all essential
details of the system had been worked out in years of practical
operation on important trunk lines of railway, so that its reliability
and ef