Beginning in the 1950s the PRSL purchased a rather modest fleet of its own diesel locomotives to replace its steam engines for passenger and freight services. When additional power was needed for the busy summer tourist season engines were borrowed from the parent corporations (usually the PRR) as was true previously with the steam locomotives. To further supplement its small fleet the PRSL made increasing use of run through power on certain freight trains to large customers that did not require classification at the PRSL's Pavonia yard.