How do you build a common access driveway on two parcels of land if the owners are the same. County will not permit without an easement.

My wife and I own two adjoining parcels of land as Joint Tenants. Topography makes it impossible to construct the driveway on just one of the parcels and maintain County standards, therefore it is our intent to construct a common access for the two parcels. The doctrine of merger would say that you may not create an easement upon your own land. My wife and I do not wish to relinquish joint tenancy, nor combine the parcels at this time. However, the County will not permit the driveway without a binding agreement between the owners of the two parcels.