Since there were four car colors, I bought coordinating solid fabric for each of them, but ultimately decided on a more limited color palette. (The royal blue coordinates nicely with the bird quilt I made for big sister two years ago.)
The blocks were easy to piece, though the scale is off as the cars are so much smaller than the roads.
I considered spelling out "beep beep" on the back of the quilt, but decided against it, so I added it to the tie instead:
Finished size: 48" x 60"