Applies to street or road construction involving subsurface work. Contemplates the clearing of the right-of-way, earth excavating and filling and grading when performed by the principal street or road contractor or other insured street or road subcontractor. Includes incidental sand and gravel digging. Also includes street or road contractors engaged in widening or changing of the line or grade of the subsurface roadbed of existing of existing streets or roads. The following should be separately rated: rock excavation, tunneling, bridge or culvert building where clearance is more than 10 feet at any point or the entire distance between terminal abutments exceeds 20 ft.; quarrying and crushing.