This a first generation smart that fared well in a rear AND front end collision at the same time. The second generation 451 available in the US should be even better.
Accidents: Smart ForTwo Punted By Delivery Truck, Returned By Van
The IIHS and NHTSA results and insurance premiums (IMO) speak well for the car as well. My insurance went down $300 per year vs a 2007 Honda Civic Coupe.
No, it's not as safe as Bradley armored vehicle, Greyhound bus, Boeing 747, Hummer H1, or a plethora of other enormous vehicles, but I'm not playing one-upmanship with my ride is bigger than yours. The smart is very safe for its size, but good people die daily in vehicles of all shapes and sizes, so you have to drive accordingly regardless of your vehicle.