Generally, if I heard the phrase brown material road, I’d assume it was some kind of Homeric euphemism for the intestine. Rest assured, however, that there is a road in California for which no one could think of a better name than this.
In a best-case scenario, the material in question could be chocolate.
I… don’t think it’s chocolate.
(Of interest, perhaps: Previous entries in the “Ha Ha — This Person’s Name” series, which long ago ceased to be strictly about people.)