Previous investigation has shown that in certain cases thermally driven wetting films may spread over surfaces without the usual fingering at the contact line. Numerical simulations suggest that the contact line region may be composed of two shock waves, a trailing Lax shock and a leading undercompressive shock, which advance at different speeds and separate. Results are presented here that show that the separation speed is indeed similar to that predicted by numerical simulations. The role of the thickness of the prewetted film on the solid surface is also investigated.