All state highways shall be maintained by the department at state expense, including sections of state highways located within local highway jurisdictions, except that in local highway jurisdictions where state highway sections are built to local highway jurisdictions standards, such as with curbs, sidewalks and areas available for parking and bus stops, the department shall maintain at state expense only the width of traveled way required for the movement of through highway traffic. The width of traveled way to be maintained at state expense shall not exceed the width of the traveled way of the state highways approaching the incorporated areas.