Again, in Classes No. 3 and No. 4 it would be legitimate to take the live load per lineal foot for the railway equal to twice the car load per lineal foot, and add thereto a small highway live load as in the last case.

Finally, in Class No. 5 it would be proper for a four-track bridge to make the live load for the trusses equal to four times the car load per lineal foot, and ignore entirely the highway live load; for the greatest combined live load would never amount to four times the car load. This was the method pursued by the author in determining the live load for the trusses of the proposed Kansas City and Atlantic Railway Company's bridge referred to in Chapter IX.