I've used this approach, yes
The kids are responsive to it & especially so when I say that they must use the booster & belt properly because I love them & don't want them to get hurt ... but the adults more or less refuse to accept the message no matter what & so they fill their kids' heads with the opposite message ~ that because they love them they want them to be able to be free in the vehicle "since it's not very likely that we'll have an accident anyway" @@
My sister & brother {well, these 2 anyway, the others are intelligent enough to appreciate the knowledge I've shared with them} anyway, my one sister & brother pair simply don't care what statistics say about anything having to do with raising kids ... for instance, their discipline borders on abuse, etc. etc. I'm kind of the FREAK in the family who actually likes to collect as much knowledge from many reliable sources as I can before puting a personal oppinion into action {or on the other hand finding out whether or not it's in our best interest to take a deeper look at why I feel certain ways about certain issues & such}, but these 2 are of the mind-set that their oppinions are all that matter no matter how many lives have been ruined from following such patterns of behavior *SIGH*
Ultimately, because of the way their visit went {in regards not only to car safety issues, but also other things} I decided to cancel our plane trip that would have continued the visit on with us spending 2 weeks at my sister's in NV. Apparently my daughter's legs have now grown too long for RF in the Wizard {2 months shy of turning 3 years old} because she's been complaining of the straps hurting & when I pulled down her pants to look there were red creases on her thighs ~ so I did end up turning her FF, but I don't blame my sister's annoying comments for it. However, it was really very difficult for me to hold my tounge as much as I did during their visit ~ I continued to share tidbits of CPS facts, but it all went in one ear & out the other & she refused to let her kid ride with me when she saw the Husky =/
So, the whole thing ended on a bit of a sour note, but at least I didn't let her ignorance overpower my convictions to provide a safe environment in situations that I AM able to control ... when my kid is old enough to understand the concept that different families have different rules {because she's not a daycare kid & has not been exposed to such differences in family dinamics before this & didn't respond to it very well this time} then I'll rethink making a trip out to my sister's, but not while my daughter is still so impressionable. UGH - family!!!!!