It has a rock road leading to it and I own the area totaling about 48 ft between 2 houses with which I could build a roadway.

For more than two decades, Southern California transportation officials have pondered how to accommodate the roadway’s swelling truck and automobile traffic, and they’ve always come to the same conclusion: We need a bigger freeway.

A 14’ tall overhead door will allow anything that can be hauled or driven on roadways to go under the door and the 16’ is needed to allow for enough door clearance.

The rivers, hills, major roadways and busways will normally mark a sub market shift regardless of zip code. 

You could also use an easement for ingress and egress, but if it were me, I would want full ownership (fee simple ownership) of the 30 feet wide strip of land used for roadway purposes.You will need a "legal description" for the lease, so see a lawyer and, if necessary, a surveyor. 

Basically the tax maps show the roadway ending even with our property line despite the physical road extending another 50-70 feet.

In case you have to trench utilities under the roadway....

Also the owner of the roadway (town, county, state?)

These are trench drains, picture shows grates on it, you can get them with flat plates as well.as far as the site elevation, usually the heights will be represented in feet like this drawing, see the 833.39 ( represents highest point) next is 831.51 then 829.64, this shows the sewer line pitches down. they also have here by the 833.29 the number 834.56, that's the grade of the road way, even though the two numbers are not next to each other, it could be assumed the storm drain is one foot lower than the road way ( 834 - 833 )

Neither of them were digital but both on main road ways with great daily car counts.