[3][4] The departments were established as the incoming Stevens Government and its Minister for Transport Michael Bruxner sought to reorganise the management of the road network in NSW.

[5][6] The Transport (Division of Functions) Act of 1932 provided for the appointment of a Commissioner of Main Roads who held the powers necessary to manage the major highways of the state.

For much of its existence the DMR undertook a significant proportion of its road and bridge construction and all its maintenance activities using its own labour force.

It also operated major mechanical workshops, asphalt plants, spray sealing crews, road linemarking teams and materials testing laboratories.

In the later 1970s and through the 1980s successive waves of internal re-organisation led to more work being let out to contract with the total employment number dropping to 8,700 by the time the Department ceased to exist in 1989.