Continuously Welded Rail Expands by Miles Without Gaps Engineering Fact
Traditional rails clicked because of expansion gaps. Modern continuously welded rails (CWR) can run uninterrupted for tens of miles. Instead of buckling freely in summer heat, the steel is prestressed before installation ("hydraulic rail stressing") to a neutral temperature of roughly 27°C (80°F) and pinned down into crushed stone ballast weighing tons per yard. In extreme heatwaves exceeding 50°C rail temperature, maintenance crews paint the rail shoulders with white lime wash to reflect solar radiation.