Crumb rubber and short fibres are introduced into the epoxy polymer core of composite railway sleepers to reduce cost and improve mechanical performance. The study investigates the effects of increasing content of crumb rubber, chopped glass fibres and polypropylene fibres. The experimental results including the microstructure of the polymer mixes demonstrate that short fibres enhanced the flexural and shear performance while the crumb rubber improved flexibility of polymer mixes. A simplified prediction equation was proposed to predict critical properties using the compressive strength. Analytical Hierarchy Process was also implemented to determine the most suitable polymer mix for the railway sleeper application.