I am Canadian, and have my girls in Frontier XT's. Summer is five and a half, and she can buckle and unbuckle herself with no help. I don't loosen the straps at all. She does her car seat and positions her chest strap herself. I double check everything. Leah who is four today!!! can buckle herself in, sometimes has problems with one of the lower clips, but other than that does it herself, and as with Summer I just check everything on her. She however doesn't have strong enough hands to unbuckle herself. She requires help. My girls can buckle themselves in where there harness is tight, but my sister needs to loosen the harnesses on the seats when she puts the girls in, cause she can't get them buckled.