That's wise. I'd never drive a car through there, it's too heavy. The ground could literally swallow it up. I wouldn't walk through either Imagine getting CO poisoning before you could escape!?!
Only an ATV would do.
There was a great little website with an amateur short film I saw not too long ago. I wonder if anyone has the link.

The above image is highlighted to point out the visible hot spots that burn close to the surface. Often the smoke and steam is quite visible. The ground is typically hot and all vegetation is dead. These areas are prone to subsidence, noxious fumes and high levels of carbon monoxide. The area at the top of the photo is the most visible. The fire burning below has recently encroached into the cemeteries. The area in the lower half of the image is a hillside along the old section of Rt. 61 where the fire has burned enough coal to cause subsidence that damaged the roadway. A large crack has opened up in the roadway, which bellows smoke and steam continually.
http://www.offroaders.com/album/centralia/virtual.htm