The use of cased carrier pipe for pipelines crossing under highways and railroads has been common practice in the industry. The first cased crossings were made using large-diameter pipe. The carrier pipe was mechanically coupled and pushed through the casing, and the coupling or collars were in direct contact with it. When coatings came into general use, isolating spacers were made of hemp rope saturated with pipe-coating enamel. End seals consisting of either concrete or pipe-coating enamel were poured into each end of the casing. The current practice of installing cased carrier pipe has changed only slightly since the beginning of its use. External loading of the carrier pipe has now been eliminated by the installation of heavy-wall casing pipe, and isolating spacers are used to prevent electrical contact between the casing and the carrier pipe. End seals are used to keep electrolyte (e.g., mud, water) out of the annular space between the carrier pipe and casing.