Gauge of track,............................. 4' 8-1/2" 4' 8-1/2" Distance between backs of wheel flanges,.... 4' 5-3/8" 4' 5-3/8" Height of truck center plate above rail, car body loaded with 15,000 pounds,....... 30" 30" Height of truck side bearings above rail, car body loaded,.......................... 34" 34" Wheel base of truck,........................ 6' 8" 5' 6" Weight on center plate with car body loaded, about............................. 27,000 lbs. Side frames, wrought-iron forged,........... 2-1/2" x 4" 1-1/2" x 3" Pedestals, wrought-iron forged,......................... Center transom, steel channel,.......................... Truck bolster,.............................. cast steel. wood and iron. Equalizing bars, wrought iron,.......................... Center plate, cast steel,............................... Spring plank, wrought iron,................. 1" x 3" white oak. Bolster springs, elliptic, length, ......... 30" 32" Equalizing springs, double coil, outside dimensions,................... 4-7/8" x 7-1/2" 3-5/8" x 6" Wheels, cast steel spoke center, steel tired, diameter,.................... 33-3/4" 30" Tires, tread M. C. B. Standard,......... 2-5/8" x 5-1/4" 2-5/8" x 5-1/4" 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.