I've had so much fun using these activities with my students; I just had to share. Each page of the book is a detachable, full-sized card with a letter, number, or shape that looks like a road. I love to have my students drive toy cars along the road in the shape of the letter/number to get familiar with the form of the letter or number in a fun way.
What's helpful is that the cards have a "green light" printed where the child is supposed to start tracing the letter and a "red light" where the child is supposed to stop tracing to finish the letter.
After the students have driven the toy car over the road, you can also have them trace the letter or number with a dry erase marker (if you've put the page in a sheet protector).
If your student wants to only play with the toy cars instead of tracing the letters, that's fine. What you may want to do is use a first-then chart to show them that they will first trace the letter with the car, then they can play with it how they choose. To use a first-then chart, you can put a photo of tracing the letter in the first box and a photo of playing with the cars in the second box. This works best if your child has used a picture schedule before. If your child hasn't used a picture schedule before, see this blog post on how to teach using a picture schedule.