While the National Highway Traffic Safety Administration (NHTSA) hasn’t tested the R-Class, the Insurance Institute for Highway Safety (IIHS) has, and the results weren’t as good as anticipated. The R-Class got a "good" rating for frontal impact from the IIHS, but its "acceptable" rating for side impact—indicating a higher chance of bodily injury—wasn’t impressive in a class nearly full of vehicles that achieved nothing but top ratings. The R-Class did, however, see a "good" rating in the IIHS’s seat-based rear-impact test. One note: Mercedes has made some running changes, and 2009 models manufactured after September 2008 were retested for a rating of "good."
That aside, all the top safety equipment is in the R-Class. Edmunds says that all Mercedes-Benz R-Class models are "outfitted with stability control with a rollover sensor, antilock disc brakes with brake assist, active front head restraints, side-impact airbags for front and second-row passengers, and side curtain airbags for all three rows." Cars.com reports several standard active Mercedes-Benz R-Class safety devices, including "side curtain airbags protect occupants in all three rows of seats, and door-mounted side-impact airbags for front occupants."
According to Edmunds, the 2009 Mercedes-Benz R-Class' "steeply raked windshield affords excellent sight lines." However, Cars.com expresses some concern over Mercedes-Benz R-Class visibility issues: "a nest of headrests impairs the rearward view, which is otherwise OK and helped by ample mirrors...reflections are evident in the steep windshield, but they're not too distracting."