The standard length of a tie is 102 inches. In specialized cases they may be longer, to spread the weight of the rails over a greater surface area. Longer ties are used in areas where the ground is soft and the stability of the rails would otherwise be a concern.
A standard railroad tie is nine inches wide and seven inches tall. Rails, however are not all identical because of milling and may very in size, up to 12 inches wide and nine inches tall.
The gap between rails is typically 12 inches so that the distance from the center of one rail to the center of the adjacent rail is approximately 21 inches.
