This worked well but was rather un-interesting. Then my friend Angela gave me a kit from a science fair at her little girl's school based on the Bloodhound SSC. The link to their pdf is here.
I needed something a little more road based for the motorway theme though so I used their basic concept and merged it with clip art to create my family style balloon powered car. I recruited friends and Eden's nursery into saving milk bottle lids for the wheels!
My design is available for you to download here for the inside and here for the outside.
So in total you will need 1 or 2 skewers, 2 straws, the printed template on both sides of A4 card, 4 milk bottle tops and a balloon.
The non-balloon straw was cut in half and then taped to the front and rear axel marked on the template. Half a BBQ skewer threaded through each straw with a bottle top pierced on the ends.
Here we are having fun making them at the party - too quick for an action shot though!!