[Tijeras_Slim]

I remember seeing lots of clamshell drives and roads growing up in Easton.

[Heatseeker]

Yup - up until a few years ago it was very common here - my grandfather's long lane was mostly clamshells.

In fact in the town I live in (Denton) there was an old plant that manufactured clothing buttons by punching them out of the shells. Its parking lot (it's now an office building) is the only one with clamshells now that I know of.