If you don't want spoilers for anything Cars Land related (pun intended), then don't read.
While waiting in line for RSR, I managed to use my trusty mobile device to identify some of the songs played in the queue. I only recognized one song personally. And my app (Soundhound) didn't recognize a few, so this is not a complete list.
Song title - Artist
Hello, I'm a Truck - Red Simpson
Hot Rod Blues - The Southernaires
Auto Conga - Xavier Cugat and His Orchestra
Heavy Traffic Ahead - Bill Monroe and His Blue Grass Boys
Car Song - Woody Guthrie
Wildwood Flower - The Carter Family
King of the Road - Roger Miller
I heard King of the Road outside in the extended queue, so I don't know if that necessarily played in the actual queue. Please add to the list any songs I missed.