This paper deals with the design and development of improved rail sections by the Denver and Rio Grande Western R.R., as an outgrowth of photoelastic stress analysis techniques which were applied to the study of rail loads and stresses. Various factors related to rail service life and rail failures are discussed, together with various nondestructive testing and inspection techniques utilized by the Rio Grande Railroad to detect such failures in their incipient stages. Some of the unsolved problems relating to rail testing and inspection are also presented.