The class D3 consisted of 22 2-6-4T tank locomotives built by Robert Stephenson & Co. between 1907 and 1914. They were built for suburban services on the coast line south of Colombo. To ensure sufficient acceleration with trains of up to 14 coaches, the drivers had a diameter of only five feet. When they were superheated, they became class D2. Twelve were rebuilt into class D1 in 1930. The five original class D1 locomotives had been delivered by Robert Stephenson & Co. in 1928.