Implication vs. Necessity
The difference between easements by implication and those of necessity can be succinctly described as follows:
To create an easement by implication, one must prove that (1) there was a unity and subsequent severance of title with respect to the relevant (i.e., dominant and servient) parcels; (2) the use established by the owner must be so long, continuous and obvious or manifest that the use indicated that it was meant to be permanent; and, (3) such use must be necessary to the beneficial enjoyment of the land retained.
To create an easement by necessity, one must show (1) prior common ownership of both parcels; (2) a transfer of one of the parcels; and, (3) at the time of the transfer an easement over the property as absolutely necessary.
An easement arises by implication where from the surrounding circumstances it is reasonable to assume that the grantor intended to grant such an easement. For example, where property is shown on a subdivision plan, a grant of a lot within the subdivision will, by implication, carry with it a grant of rights in the streets and ways to the extent necessary for ingress and egress to and from the lot. This implied right is one in the nature of an easement. (This right should be distinguished from the right in the fee that necessarily passes to the grantee under G.L.c. 183, §58 sometimes called the derelict fee statute. That statute places the fee immediately adjacent to the lot in the grantee, thereby effectively "accounting" for it so that it is not "forever lost" with the developer of the subdivision.) The easement right has been recognized for centuries, and at one time permitted the grantee to "prospect" around the subdivision, giving to the grantee rights to use all the roads therein. The right, although still recognized, has been limited to the use of the roads that provide immediate access to the lot over the shortest distance to a public way.
An easement by necessity arises not because it is implied from the circumstances of the conveyance, but rather because access otherwise denied would precipitate irreparable harm. If the owner of land conveys out the fee in that portion of the property located between a street and retained back land the back land will thereby become landlocked. The law will not permit this to happen, as is stated in Restatement of the Law of Property - Servitudes, §476:
If no use can be made of land conveyed or retained without the benefit of an easement, it is assumed that the parties intended the easement to be created. This is true not only where it is claimed by the conveyee but also where it is claimed by the conveyor. It is assumed that the parties could not have intended that the land retained by the conveyor should be useless in his hands . . . .
Not only may the implication arise in favor of the conveyor when a prior use has been made, but it may arise even though no use of the land corresponding to the use claimed had ever been made prior to the conveyance. The fact that the use claimed does correspond to a prior use is a circumstance contributing to the implication of the easement." (Emphasis added).
Based on the foregoing, the use of a strip over which a road runs for street purposes before the conveyance was made would be consistent with the retained right of access. The theory has been followed in Scagel v. Jones, 355 Mass. 208, 243 N.E.2d 908 (1969). See also the memo, Reference to Plan, in Easements.