Subsequent to the crash testing, design modifications were made to the swing-away mailbox support by MINNCOR Industries. There was a need to evaluate these design changes through full-scale crash testing to determine whether or not they adversely influence the crashworthiness of the mailbox system.

    The only suitable method for evaluating any change in impact performance associated with these design changes is full-scale crash testing. In the previous testing performed on the original swing-away mailbox design, substantial windshield damage was observed. Since NCHRP Report 350 does not provide objective criteria for assessing windshield damage and there is no other windshield damage criteria for mailboxes, the Federal Highway Administration stated that the results of the crash tests on the modified design will be considered acceptable if the windshield damage and potential for occupant compartment intrusion “is no worse than that caused by the original MinnDOT design.”

    The objective of this project is to crash test the MinnDOT swing-away mailbox support as modified by MINNCOR Industries and determine if it complies with recommended criteria for breakaway supports contained in NCHRP Report 350. The evaluation consisted of two high-speed crash tests in which the mailbox support system was impacted at two different locations. The impact conditions followed those of NCHRP Report 350 Test Designation 3-61, which consists of an 820 kg (1800-lb) vehicle impacting head-on (i.e., zero degrees) at a speed of 100 km/h (62 mph). The modified MinnDOT swing-away mailbox assembly meets the requirements of NCHRP Report 350 as a Test Level 3 (TL-3) breakaway support structure.

Minnesota Swing-Away Mailbox crash test report
(Limited access file - password protected)