Help, how can i stop my toddler getting his arms out of his car seat straps

My little boy is 2 1/2 and for the last few weeks keeps getting his arms out of his stage 1 car seat straps while i'm driving. I have to stop to put his arms back in and i tighten the straps as tight as they'll go but he still manages it!



I tried putting him in a stage 2 car seat as he's the right weight but he just takes his arm out the seat belt.

I'm getting so worried as its so dangerous and its not always possible to stop the car straight away and he normally just takes his arms right back out again anyway.



What can i do, is there anything i can get that'll stop him doing this and keep him strapped in properly? I even borrowed a different car seat from my sister and he took his arms out of that one too