How these routes evolved into routes operated by IPTC, is covered at the Route History page.
L. J. Smith Transportation Co. - incorporated 1937 as reorganization of Logan J. Smith's jitney and charter bus operations. Sold to Indianapolis Railways/People's Motor Coach Co. in 1941, operated bus routes serving Sunshine Gardens and operating via Kentucky Ave. Both routes were discontinued shortly after World War II.
Suburban Bus Co. - Indianapolis Street Railway Co. subsidiary formed in 1931 to operate local bus service, replacing discontinued Terre Haute Indianapolis & Eastern Traction Co. interurban trains, and operating via Washington St. and Rockville Rd. west of Indianapolis. Subsdiary absorbed into main company in 1941, and route sold to Danville Bus Lines in 1950.
Post Way Transit, Inc. - acquired by Indianapolis Railways in 1944, one route operated mainly via east 10th St., discontinued in 1952 as largely redundant to existing routes.
Central Swallow Coach Lines - began operating buses as early as 1935, east of Indianapolis to Dunreith and New Castle, replacing the THI&E railway line which had been abandoned in 1932. Now part of the IndyGo Washington route.
Suburban Lines, Inc. - began operating buses south of Indianapolis to Greenwood and Franklin in 1941, replacing the former Interstate Public Service Co. railway line which had operated to Seymour and Louisville. Now part of the IndyGo Madison route. Added new route north to Zionsville by 1949, now part of the IndyGo Michigan route.
Indianapolis Transit, Inc. - began operating after World War II west to Plainfield, providing local bus service along the abandoned former THI&E railway route towards Terre Haute. In 1950, acquired two Indianapolis Railways extension bus routes connecting with the west Washington St. trolleybus route. By 1968, Indianapolis Transit, Inc. acquired the Danville Bus Line, which had begun operating buses between Indianapolis and Danville in 1936, replacing the THI&E railway line which had been abandoned in 1930. Now part of the IndyGo Washington route.