Which of the following reason(s) support(s) the usage of sleepers below the rails?

(A) To reduce the pressure
(B) To increase the normal reaction
(C) To increase the surface area
(D) To accommodate the thermal expansion/contraction of the rails

Solution

$P_{Rails} = \frac {Weight\, of \, Train}{Effective \,  Surface \, Area} $

Sleepers increase effective surface area thereby reducing pressure on the rails which otherwise are quite narrow.

Hence, (A) & (C)