Is there child car seats which i can use the lap(centre) belt.?
Yes this is the best way. The lap belt should only be used to secure a car seat that uses a harness. Lap belt only is not safe to use with a booster or even for an adult. I would keep your 3 year old in a harness for as long as possible and then you’ll need to find out if you can get a shoulder belt retrofitted or look into different vehicles. Many car seats will harness to 65 and even 80 lbs, so you should be able to make it at least 3 more years, probably longer. Not all lap belts will lock properly to hold the car seat in, so that is something else to consider. Is the latchplate (the part you slide into the buckle) sewn onto the belt? Or is there a part that the belt is threaded through and you pull on the excess to tighten it? If you have the second type, you should be fine. If you have the first type, you’ll need to do an additional test to see if the belt is safe. Pull the belt all the way out. Now slowly let a small amount of belt go back in Do you hear a slight ratcheting or cl
