In addition to notifying NHTSA (or Transport Canada) in a situation like this, please notify General Motors.

Call 1-866-HUMMER6 (486-6376), or write:

HUMMER Customer Assistance Center
P.O. Box 33177
Detroit , MI 48232-5177

In Canada, call 1-800-263-3777 (English) or 1-800-263-7854 (French), or write:

General Motors of Canada Limited
Customer Communication Centre CA1-163-005
1908 Colonel Sam Drive
Oshawa , Ontario L1H 8P7