What I'm after is the sort of drain that is composed of concrete slabs that have a slight v in them or a shallow u shape, like the drains often found in a low point going across a road. So each piece would be about say 3 feet wide by 3ft or more long and maybe 2in thick with say a 2 in shallow v dipping to the center so 4 inches deep overall.
A triangle of a 36 inch wide cross section would give the other two sides as about 18.1 inches and the obtuse angle between them as about 167 degrees. A simlilarly shallow u shape would also work and seems more common in the roads.
Someone out there must make these as I see them in the roads and I doubt they are custom.
Once I have a name for this type of drain it will be much easier to find a supplier. Any ideas?