Discussions

My child continually unbuckles herself from her car seat while we travelling anywhere - is there anything that I can get that will prevent her from unbuckling?

Anything you add could affect how the seat performs in a crash or the ability to get the child out of the car quickly in an accident. If you have Facebook, seats for kids discussion group is a great resource. I've seen this topic come up a couple times and if the child is old enough, the best bet is to explain the consequences. Some parents scare them so they stop. Others use discipline/ reward systems. If they're too young for that, you can also reach out to the car seat manufacturer in case it's an issue with the seat making it easy to undo.

What kind of seat is your child is, and how old are they? Are we talking about a forward-facing seat with a 5-point harness, or a booster seat?  
 
My experience with 5-point harnesses is that the buckle is generally too difficult for a young child to unbuckle by themselves (even though it's relatively easy for an adult - just the differences in strength). If they are unbuckling it themselves, maybe it's a problem with the seat or you should consider getting a different seat that's harder to unbuckle.  
 
Also, make sure they're in an appropriate seat. A child under 5 should not be in a booster seat, according to provincial rules. If you've moved your child to a booster seat early due to weight/height issues (such as a 2-3-4 year old), you need to purchase a forward-facing 5-point seat with a higher height/weight capacity. They exist, but usually cost more. Not only is it the law, but your child will be safer at that age and it may resolve your problem if that's the case.  
 
I have had issues with both my neurotypical and autistic kids unbuckling themselves while driving, and the car *stops immediately* if that happens, and we don't move until it's done back up. Repeat process ad nauseum. By 5, most neurotypical children catch on pretty quick. Pain in the butt for the adult driving (and it may take awhile to get anywhere initially), but worth the effort.  
 
Check out the resources mentioned above. If it's a young (age 2-3) child in an appropriate seat for their age, they will likely have fantastic ideas about how to work with your child to train them to stop doing that.