Different road surfaces

[pokerjoke]

Driving in the pouring rain last night on the motorway between junctions 25 and 31 of the M5.
I noticed the difference in spray on certain sections.
In places you couldnt see a thing,very dangerous conditions,then all of a sudden there was less spray
even though the rain was the same strength.
Ive noticed before the difference in road surfaces.
Does anyone have any experience in this department,and why cant the same splash free surface be used all over.
Im sure its down to cost,or lack of materials.

 

[Lump]

I tend to find concrete motorways give off alot more spray than tarmac. The M5 is mostly concrete if I remember my roads correctly.