Which best explains how railroad companies were able to standardize their timetables in 1883? .By combining into a single railway company
.By working together voluntarily
.By unionizing their labor forces
.By complying with federal legislation

By working together voluntarily

Explanation:

Before the current time-zones in the United States and Canada came into effect, the various towns and cities had their own times depending on the position of the sun amongst other things. This made scheduling a nightmare for the Railroad comapnies who would have to list multiple times for the same train.

Burdened by this and powerful enough to change it, the Railroad companies met and decided to work together voluntarily to divide the United States and Canada into 4 zones which were quite similar to the ones in use today. These zones went into effect in 1883 and were officially adopted by Congress in 1918.