I grew up in the town closest to Sevier Lake (Hinckley Utah). Over the years I've tried to drive on the lake bed several times. The problem I found is that the lake bed never completely dries out. I would invariably break through the dry crust and get into really tacky alkali mud.
Now a few miles west of Sevier lake is a hardpan called Ibex hardpan. It does dryout and if I remember is about 6 miles long. (Don't hold me to that number since I haven't been to Ibex in years and, even in the desert, things change over time.) I need to go have a look this summer.