Mile Markers on Interstates

Hi all,

I was curious as to whether anyone knows if Mile Markers are available anywhere either as a POI or actually on any mapping software (google maps, map quest, etc).

One of the main reasons that we still don't use GPS on fire departments is besides the fact that our maps are more accurate (numerics-wise), they also come pre-made with mile markers. Sure, we have to input our own "POIs" for things like fire hydrants and interstate turnarounds, but does anyone know if milemarker files are commercially available?

-Wu