This document discusses different classifications of railway transportation systems. It describes railway classification by track route including main lines, branch lines, and yards. It also discusses railway classification by system including surface railways, elevated railways, underground railways, and tube railways. Further classifications covered are by locomotive system including electric, diesel, and gas locomotives. Additional classifications mentioned are by track types such as double headed rails, bull headed rails, and flat headed rails as well as by sleeper including wooden, metal, and concrete sleepers.