In 1973, transit authorities statewide would finally be granted a much needed ongoing source of funding from the state. On December 31, 1972, the Michigan State Legislature would amend Act 51 of the Public Acts of 1951 with the passage of Act 327 of the Public Acts of 1972, which was signed into law by Governor William G. Milliken on January 3, 1973. This amendatory act would finally provide eligible state transit authorities with a guaranteed source of funding by establishing a separate Statewide General Transportation Fund created within the state's Motor Vehicle Highway Fund. This newly established form of revenue would be largely funded by an additional 2-cent per gallon gasoline tax, with one quarter of that money (½-cent per gallon) slated for mass transit operations and capital improvement usage. Though far short of what would be needed to provide a fully-funded regional system, this funding allowed SEMTA to begin making substantial progress toward achieving its goals.

Meanwhile, by the early seventies, a number of transit bus companies in the area, including the Detroit DSR (whose ridership numbers had dropped 25% in five years), were facing huge revenue loses and possible bankruptcy. With the state's new gas tax funds, SEMTA was able to enter into a number of short-term "purchase-of-services" agreements, where SEMTA would pay the local bus companies for maintaining service on their own routes. This arrangement managed to keep those companies in operation until many were later bought-out by SEMTA. This type of arrangement would also kept the Detroit bus system in operation through the remaining DSR years.

Purchase-of-service agreements were also used by SEMTA to launch a series of Direct Access Shuttle (DASH) routes to directly link a suburb to an automobile related employment center. Purchase-of-service agreements would also be used to relaunch suburban bus routes along Middlebelt and Twelve Mile roads that had recently been discontinued by the DSR. It was also during this period (1974) that SEMTA purchased five used 1965 GM model TDH-4519 "New-Looks" from the Evanston (Ill.) Bus Company to upgrade its Lake Shore Division fleet, and seven former Greyhound GM model PD-4106 highway (parlor) coaches that were assigned to the other divisions.

Purchase-of-service agreements were also used after SEMTA took over operation of the city of Pontiac's bus lines. After Pontiac cancelled its service contract with the Pontiac Transit Corp. (American Transit Corp.) in late 1970, that city's Department of Public Works took over the bus routes effective February 2, 1971, operating as the Pontiac Municipal Transit Service. New coaches were purchased and the four routes were combined into two. However, effective July 2, 1973, the small city-run system (including drivers) was transferred-over to SEMTA, which would use purchase-of-service agreements with Great Lakes Transit to operate the two former Pontiac routes.