Beginning with the 1970's, some of the municipal transit agencies faced rising demand for service and had to consider system expansions and even entirely new services such as a light rail or commuter system. For even a major, multi-year project it may not be economically viable to employ and train all of the skill sets necessary to implement a new transit operation. Services that are contracted include planning, environmental analysis, architecture/engineering, and construction. In a few cases, this has included the entire range of activities-Design, Build, Operate and Maintain (DBOM). This is described further under innovative procurement mechanisms.