The North Dakota legislature recently passed a law to exempt the state's agricultural truck fleet from a requirement for rear-guard equipment as federally mandated large trucks. This analysis presents the public safety benefit-cost assessment of the device in terms of crash injury severity associated with agricultural truck rear-end crashes. It is based on North Dakota truck crash data and other research conducted on this type of crash where the passenger vehicle collides with the rear of the truck. The injury avoidance benefits and commercial vehicle safety grant benefits are estimated to be $11.4 to $20.2 million over the seven-year depreciable truck life. These public safety benefits are substantially higher than the estimated lifetime cost for the rear-guard equipment and maintenance of $8.1 million. In addition to the substantial public safety benefit, noncompliance with the federal mandate may be result in the loss of certain transportation infrastructure funds.