The design speed of two-way 8-lane expressway is 120km / h, and the general value of subgrade width is 45.00m. Who knows how to get the value?

The design speed of two-way 8-lane expressway is 120km / h, and the general value of subgrade width is 45.00m. Who knows how to get the value?

General subgrade width of Expressway two-way 8 lanes: 0.75m (earth shoulder) + 3.0m (hard shoulder) + 4 × 3.75m (carriageway) + 4.5m (median) + 4 × 3.75m (carriageway) + 3.0m (hard shoulder) + 0.75m (earth shoulder) = 42.0m
For 45.0m integral subgrade, the width of subgrade may be adjusted when it is shared by city and transit, or the median may be widened in order to strengthen the landscape. Personal opinion: when the carriageway is not compressed, the shoulder and median can be adjusted appropriately