Provides recommended guidelines for the safe lowering of pipelines (e.g. at crossings by new roads and railroad lines) without taking pipelines out of service. In conducting this study, a method was developed to calculate stresses induced into a pipeline as the result of lowering it. Simple computer programs were developed to calculate: 1. Stress added as a result of lowering. 2. Intitial axial stress existing prior to lowering (requires lifting the pipeline and making certain measurements). 3. Trench of profiles that limit the added stress to a desired value. 4. Temporary support spacing and allowable differences in support heights. The study also addresses safety issues associated with lowering a pipeline in service. Recommended procedures for lowering are provided and the limitations on lowering are discussed. The study was jointly funded by the U.S. Department of Transportation, the American Society of Mechanical Engineers, and API.