I've driven over this bridge several times, and each time I thought that you really do need a truck to take the "Truck Route". No way my minivan could make it....(at least not when it's muddy)
It's a camouflaged peanut butter jar mini Altoids tin, magnetically attached to the guardrail. I enjoy exploring the old highways, and this qualifies as a unique spot along old Hwy 6 & 50. Take either the Mack exit from Colorado or the Westwater exit in Utah to get here. The road is in pretty bad shape, but I made it through the mud in my minivan. (It's been dry every time I have been out here for maintenance, and there are no problems when it's dry!)
UPDATE! - 4/17/12 - The bridge has been fixed and the truck route is gone. The cache is still in good shape though and will remain in place!
UPDATE - 10/3/2025 - New container, new location.