State highways in India are numbered highways that are laid and maintained by the state governments. These are not related to National Highways and are not maintained by the National Highways Authority of India or the central government in any way. The state highways are usually roads that link important cities, towns and district headquarters within the state and connect them with National Highways or highways of neighbouring states. These highways provide connections to industries or places from key areas in the state making them more accessible.
References
State highways in India Wikipedia(Text) CC BY-SA