INDOT keeps traffic counts on State and National roads, but also has many traffic counts on other main roads that are not state-owned roads. Their website has an interactive map that allows you to see where the traffic count stations are. Click on the icons. Make sure you check the "Non-State Owned Routes" box to get all the count stations.
Columbus and CAMPO keep traffic count data for local and county street, and can provide it upon request. The following map, which is supported by a private entity, has many of the traffic counts done locally on a map.