What Azari said is correct. The concrete ramp grooves line IS NOT FOR SHOWING direction. It is for dispersing the rain water to avoid slippery during rain / wet condition. It MUST be face upward so that when there’s rain water, it should direct the water to the left or right side of the longkang.

If you make the groove line facing downward, majoriry of the water will end up meet at the center of the concrete which will result hazard for a car going down or up.

This is basic engineering mate, if you know nothing, just shut up.