That's what you find in the two tunnels of the abandoned section of the PA Turnpike. I rode through them back in September. One is nearly 3,800' and the other is around a mile. Outside it was mid to upper 80s in the shade. Felt hotter with sun beating down on me and with the humidity. It was easily 20 degrees cooler inside the tunnels. Even standing at the mouths you felt like you were standing in from of a central AC system.