I recently had the chance to try out Paper Trax, a fun way to create tracks for cars without them constantly being underfoot. They were developed when the creator's son wanted a track for his car, so his dad made one out of a cereal box.
These tracks are easy to use. They come with adhesive that won't damage walls when removed, are durable enough to hold cars, but can be recycled when done. They fit Matchbox and Hot Wheels cars and other similarly-sized vehicles, and can be customized along the walls exactly how you want them to go. There are even corner pieces that allow for turns in the room's corner. My daughters and nephew had a blast setting them up and playing with them - see them in action in the video below!
Paper Trax can be purchased on Amazon.com and select retailers in California and Arizona.