I think a tractor is a better investment than gold or silver.
Anything that can be used to create "value." All things of that nature have been going insane in value.
By the time SHTF, a tractor will be worth 5-10 tanks.
You have fun running that dozer down the pavement.......let me know how many fillings you lose in the first mile.
Also dozers really can't get good traction on pavement...large tractor would probably get better traction, better milage, and less maintenance costs than a dozer...just my two cents.