Building a Subway Under a Subway 



Little do New Yorkers know that they are traveling on 

 a suspended subway even though it is underground 



By Howard B. Gates, C. E. 



MANY residents of New York city 

 no doubt remember the time when 

 the possibilities of subways as a 

 means of rapid transit were as little 

 realized as the practical application of 

 the airplane, in its present development, 

 is now considered, to our everyday life. 

 But within the last fifteen years a most 

 wonderful system of subways, comprising 

 more than two hundred miles of under- 

 ground railroad, has been built in New 

 York under enormous difficulties at an 

 expenditure of more than $400,000,000. 



Statistics show that nearly 2,000,000 

 persons are carried by this system every 

 day and that m.ore than seventy-five 

 per cent, of this number seek its ac- 

 commodation between the hours of six 

 and nine o'clock in the morning and be- 

 tween four and seven o'clock in the 

 evening. One of our 

 largest railroad systems, 

 with some 26,000 miles 

 of track and traversing 

 thirteen states, carries 

 but one-third of this 

 number. During "rush" 

 hours, even standing 

 room is at a premi- 

 um, although ten-car 

 trains, each carrying 

 2,000 persons, are oper- 

 ated under a one-and- 

 one-half-minute head- 

 way, controlled by elab- 

 orate electrical signal 

 and emergency stop de- 

 vices, all of which must 

 operate perfectly to 

 make this service pos- 

 sible. 



The difficulty of con- 

 structing such an im- 

 portant and complicated 

 system through any of 

 New York's busy thor- 

 oughfares, loses much in 

 a comparison with the 

 difficulties of Iniilding 



Diagram showing relative locations 

 of the old and the new subways 



such a structure beneath an existing and 

 operating subway, without entering or 

 disturbing the structure above. Al- 

 though the average weight of the subway 

 may not be more than a ton to the 

 square foot, there are points, at the 

 columns for instance, where concentrated 

 loads of two hundred or three hundred 

 tons, together with adjacent heavy and 

 rapidly moving trains, make any dis- 

 turbance to the equilibrium or stability 

 of the temporary or permanent supports 

 a matter of considerable responsibility 

 and concern. 



Such a piece of work is now in progress 

 beneath the present Times Square sta- 

 tion at 42nd Street and Broadway, 

 passing diagonally beneath that station 

 for about 250 feet of its length. Any in- 

 terruption to operation at this point 

 would congest the 

 entire system, and 

 yet, under a con- 

 siderable portion 

 of that structure, the 

 original foundations 

 have been supplanted by 

 a complicated system of 

 steel beams and timber 

 supports. Traffic is 

 maintained and the 

 300,000 persons who use 

 the subway daily at that 

 point do not even know 

 what is going on beneath 

 them. The new struc- 

 ture also has four tracks, 

 two local and two ex- 

 press tracks, and will be 

 operated by the Brook- 

 lyn Rapid Transit Com- 

 pany. Connecting pas- 

 sageways will lead from 

 the transit company's 

 present, recently com- 

 pleted station on Broad- 

 way between 40th and 

 42nd Streets to the Inter- 

 borough station above 



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