Keep daughter from unbuckling carseat?

Hannah

My daughter is 3 and doesn't really understand the danger of vehicles yet. She recently learned how to unbuckle her own carseat and slide the chest strap all the way down to her waist. She usually does this when we're on a car ride for longer than 10 minutes, and does it so quietly we don't notice until she's trying to climb to the front seat. She doesn't react to any form of punishment so I don't know how to stop her. Any suggestions?