When we visited Rushmore there were tour buses sqeaking through the needles tunnel. It appeared it was done by many of the drivers to give those on board a thrill. Drivers were helping each other, seemed the most important thing was to get properly lined up on entering the tunnel as no room for adjustmen once inside. After talking with a ranger was told they seldom have trouble with the tour buses, it's the campers that see them do it and think they can.
Getting my 3/4 ton tow vehicle through was thrill enough for me!
Tim & Mary Discovery 40X. Chevy Tahoe. RVM32
"I've been lost now, days uncounted..."GFR"