I found this link after a quick Google search but did not have a chance to read the article:
Oct 20, 2006 ... to UPS employees who meet certain criteria, including seniority, ... and passing a DOT physical, which includes the DOT hearing test. ...
www.fordharrison.com/shownews.aspx?show=2475 - 71k
This is an interesting article but here in Pacific Northwest area, we have not seen deaf employees driving UPS package cars on road yet. Only in the Hubs when drive around parking lot or to car wash. Thanks for the article though.