I worked out this simple pattern for our Ravelry group, We Care - Maine, to use for our charity knitting. It is designed to be as large as possible using one 200g skein of yarn. So do not worry if it comes out a bit short. It doesn’t matter!
It has a single slot for the car seat straps to come over the top of the banket and buckle in the middle, keeping the blanket secure in place and the child warm underneath it.
Please consider knitting one for your favorite charity!