I came upon this little trick by complete coincident that I had an egg crate mattress bundle in my garage that I had bought for cake decorating. Since I had extra, I now use it for cake transporting. No more having my husband drive me to deliver one cake that has fragile pieces. I just put this egg crate mat in the back of my car and once I sit the cake on it...it stays! No sliding and the cushioning probably (I don't know I'm not back there) helps with the lumps and bumps you hit on the way to your destination. Once the cake sits on the crate it's like Velcro!
Try it..and let me know what you think!