Vast majority of Texas has to deal with caliche and clay.
Caliche is a limey crusty material usually shot through with rock that dominates western half of Texas. Clay soils dominate the eastern half of the state.
Caliche is sedimentary rock of calcium carbonate (i.e. limestone) that binds other materials such as gravel, sand, clay and silt.
Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter.
In other words, minerals and sand are primary constituents of road grime in most of Texas unlike here in Florida where oil-based dirt is more common.
Calcium carbonate and clay dissolve in acids (brake dust too) by releasing carbon dioxide. Alkaline works better on oil/organics.
So, generally speaking, acidic would be principal cleaner for touch-less process in TX.
Is two phase cleaning necessary for touchless? Yes, if the wash is located near a lot of asphalt paved roads.