Overloading of an easement is a concept that has to do with an attempt to grant the benefit of an existing easement to other land, which did not previously enjoy the right. The overbursening of an easement relates to an attempt to expand the use of the easement as to the same property but for different or expanded purposes. Apportionment of an easement involves neither the overburdening nor the overloading of an easement, but rather is the acceptable practice of "divvying up" of easement rights enjoyed by a parcel to and among the various constituent parts thereof when that parcel is subdivided into smaller portions.
Overburdening and overloading of an easement are generally unacceptable because the servient property (the land over which the easement runs) is thereby subjected to a greater burden than was originally contemplated when the easement was initially granted. That is, granting rights to adjacent property in addition to the dominant estate (the land which enjoys the easement) would involve the overloading of an easement, because now the servient property would be used to service more land than was originally anticipated. But if that is true, how is it that breaking up the dominant estate into many lots is simply considered an acceptable apportionment of existing rights? Both would result in an expanded use of the easement, but overloading would not be permitted while the reapportionment would. How is this reconciled? This is addressed in the Restatement of the Law of Property, Volume V, Servitudes:
The burden upon a servient tenement frequently will not be greatly increased by permitting an easement appurtenant to attach to each of the parts into which the dominant tenement may be subdivided. Though some increase in burden may result from the fact that the number of users is increased by the subdivision, the extent of the use is still measured by the needs of the land that constituted the original dominant teniment. Moreover, dominant tenements are ordinarily divisible and their division is so common that it is assumed that the possibility of their division is contemplated in their creation. Hence, unless forbidden by the manner or terms of its creation, the benefit of an easement appurtenant accrues upon the subdivision of a dominant tenement to the benefit of each of the parts into which it is subdivided.
But there is a presumption that an easement that does not specifically provide otherwise is nonexclusive. "[E]xclusive easements should be clearly expressed." Butler v. Haley Greysone Corp., 352 Mass. 252, 224 N.E.2d 688 (1967). The significance of this, at least in relation to easements in gross, is explored in Restatement of Law, Property-Servitudes, §493, which states:
A nonexclusive easement in gross is one which does not give, as against the owner of the servient tenement and others who may be privileged under him, the sole privilege of making the use authorized by the easement. In the case of such an easement the owner and possessor of the servient tenement has not only the privilege himself to make the use authorized by the easement, but he retains the power to create like privileges in others. The apportionability of the easement by its owner would be inconsistent with such a power in the owner and possessor of the servient tenement. Because of this, the apportionability of the easement will not be assumed in the absence of a clear indication to the contrary in the manner or terms of its creation. (Emphasis added.)
The overburdening of an easement does not involve expanding easement rights for the benefit of additional land, or the distribution of easement rights servicing land to all of the sub-portions of that land; overburdening involves expanding the use of an easement with respect to the same land but for additional or different purposes.