The width of subgrade sideline is set from the calculation starting point of road design center to both sides. Line width = 1/2 pavement design width+(pavement design elevation-original ground design elevation) * design slope ratio. For example, the road design width is 14m, the pavement design elevation is 10m, the original ground elevation is 6m, and the design slope ratio is 1: 1. Setting-out width (from road design center line to both sides) =14/2+(10-6) *1.5 = 7+6 =13m.