The cross slope of municipal roads is usually 1.5%-2%, and the cross slope of subgrade construction is usually 3%. As for +/-3%, it means that the left and right cross slope directions are all conventional cross slope directions, with the middle of the road high and the side of the roadway low. Non-reverse slope means that the elevation of the roadway boundary line cannot be higher than the standard height of the road to form a reverse 3% cross slope.
In road design, the slope of 0.3% mostly means that the road section with longitudinal slope less than 0.3% needs to be provided with zigzag street ditches, and the longitudinal slope of zigzag street ditches is 0.3%. According to the layout of rainwater inlets, the setting point is set to meet the drainage needs!
I have been doing road design for 20 years and have never heard the landlord's statement. Personally feel that there is something wrong with the statement! For reference only!