There is no simple answer to your question.
A range of values for the friction coefficient must be assumed.
Tests to determine the friction coefficient of broken glass sliding on various materials may not include the effects of vertical drop (2'-4') on the friction coefficient as well as the many variations possible with the various pieces landing on the local terrain.
Asphalt and concrete are not smooth surfaces.
Therefore to be conservative you should use a range of values for the friction coefficient.
This as well as the other comments in this thread indicate that the location of tempered glass is not a good indicator of speed.
brian mchenry@interpath.com
