You can put wooden billboards anywhere that is allowed by law. I've owned them on giant interstates and 2 lane country highways. What really limits where you can put them is the landowner -- they are not very attractive when viewed from the back or next to your building. Many locations will only financially allow for a wooden billboard and not a steel monopole.
The value of a sign is based on math and perception. If you calculate what the sign will rent for and the expenses, and then apply a cap rate to that net income, that will give you the value of a built location. Subtract the cost to build it, and you have the value of the lease and permit The perception part is what the expectation is of increasing rents, which might impact the value higher.