Plaintiff appeals as of right the trial court’s entry of judgment in favor of defendants in this declaratory judgment action. We affirm.
Defendant Stenberg Brothers leased a tanker-trailer to Mead Corporation for use as a storage tank. The tanker-trailer was built in 1955. It was designed to transport liquids in bulk, and had been used to do so until 1987. Since 1987, the tanker-trailer has not been registered and has been used solely as a storage tank. When leased by Mead Corporation, the tanker-trailer was pulled on a public highway fifteen miles to its destination and, when Mead Corporation was no *47longer in need of the tanker-trailer, it was to be pulled back the same way. During the course of the lease to Mead Corporation, defendant Ronald Budkis, who worked for Mead Corporation, allegedly sustained personal injuries as a result of falling to the ground from the top of the tanker-trailer. Defendants Ronald J. and Linda L. Budkis sued defendant Stenberg Brothers, asserting negligence and breach of warranty. Plaintiff, who was defendant Stenberg Brothers’ commercial insurer, filed this declaratory judgment action asking for a determination whether plaintiff had a duty to defend and indemnify defendant Stenberg Brothers in the underlying action. The trial court ruled that plaintiff did have a duty to defend and indemnify. We agree.
The general commercial liability policy at issue in the case at bar contained the following: “automobile exclusion”:
It is agreed that the policy does not apply to the ownership, maintenance, operation, use, loading or unloading of
(1) any automobile owned or operated by or rented or loaned to the named insured, or
(2) any other automobile operated by any person in the course of his employment by the named insured, or
(3) any mobile equipment while being towed or conveyed by an automobile, or
(4) any snowmobile or trailer designed for use therewith; but this exclusion does not apply to the parking of an automobile on premises owned by, rented to or controlled by the named insured or the ways immediately adjoining, if such automobile is not owned by or rented to or loaned to the named insured.
The policy’s definition of “automobile” is “a land motor vehicle, trailer or semi-trailer, designed for *48travel on public roads . . . but does not include mobile equipment.” According to the policy, a vehicle is “mobile equipment” if it is “not subject to motor vehicle registration.” Therefore, under the policy, if a vehicle is not subject to motor vehicle registration, it is “mobile equipment,” and not an “automobile,” which means that the automobile exclusion does not apply and plaintiff has a duty to defend and indemnify.
Under Michigan law, one type of vehicle not subject to motor vehicle registration is “special mobile equipment.” MCL 257.216(d); MSA 9.1916(d). Therefore, the determinative issue we must address is whether the tanker-trailer qualified as “special mobile equipment” pursuant to MCL 257.62; MSA 9.1862. The statute provides in part:
“Special mobile equipment” means every vehicle not designed or used primarily for the transportation of persons or property and incidentally operated or moved over the highways, including farm tractors, road construction or maintenance machinery, mobile office trailers, mobile tool shed trailers, mobile trailer units used for housing stationary construction equipment, ditch-digging apparatus, and well-boring and well-servicing apparatus. The foregoing enumeration shall be deemed partial and shall not operate to exclude other such vehicles which are within the general terms of this definition.
The trial court ruled that the tanker-trailer was special mobile equipment because, although it was designed to transport property, at the time of the incident it was not being used in such a manner and was only incidentally operated on the highway. On appeal, plaintiff claims that this ruling was error.
*49In support of its claim, plaintiff relies on Davidson v Secretary of State, 351 Mich 4; 87 NW2d 131 (1957). In Davidson, the issue was whether the plaintiffs “batching trucks,” which were used to transport concrete from a mixing plant to a paving site and traveled over public highways, qualified as “special mobile equipment.” The Supreme Court answered in the negative, stating:
The “batching tracks” were (1) designed and (2) used primarily for the transportation of property, and (3) their operation in 1955 over the service roads open to public travel was more than incidental. Existence of any 1 of these Sfac-, tors, all of them here present, will defeat the claimed exemption. [Id. at 9 (emphasis added).]
Plaintiff concentrates on the emphasized portion of Davidson and argues that in this case, because the tanker-trailer was “designed” primarily for transportation of property, one of the Supreme Court’s three factors exists and the claimed exemption is defeated.1
There is a clear conflict between the plain language of the statute and the Supreme Court’s statement in Davidson regarding the statute. Under the plain language of the statute, a vehicle is special mobile equipment if it is not designed or used primarily for transportation and incidentally moved or operated on the highway. According to Davidson, a vehicle is not special mobile equipment if it is designed or used primarily for transportation and incidentally moved on the *50highway. The conflict can be illustrated as follows: under the statute, if the vehicle was designed for such use, it could still be special mobile equipment if it is not used as such (and is only incidentally moved on the highway); whereas, under Davidson, if the vehicle was designed for such use, then it is not special mobile equipment no matter how it is actually used. The problem appears to be that in regard to the phrase “not designed or used,” the statute, on its face, promotes a disjunctive relationship between “designed” and “used,” whereas Davidson promotes a conjunctive relationship between the words. Therefore, the key to the conflict, is the interpretation to be placed on the word “or” as it appears in the statute.
The primary goal of statutory construction is to ascertain and give effect to the intent of the Legislature. Livingston Co Bd of Social Services v Dep’t of Social Services, 208 Mich App 402, 406; 529 NW2d 308 (1995). When the language used in the statute is clear, that statute must be enforced as written. Id. In construing the language of a statute, every word or phrase should be accorded its plain and ordinary meaning unless defined in the statute. Id. The word “or” generally refers to a choice or alternative between two or more things. Root v Ins Co of North America, 214 Mich App 106, 109; 542 NW2d 318 (1995). “The popular use of ‘or’ and ‘and’ is so loose and so frequently inaccurate that it has infected statutory enactments.” Id., quoting Esperance v Chesterfield Twp, 89 Mich App 456, 460-461; 280 NW2d 559 (1979). However, the words are not interchangeable and their strict meaning “ ‘should be followed when their accurate reading does not render the sense dubi*51ous’ ” and there is no clear legislative intent to have the words or clauses read in the conjunctive. Id.
In our opinion, a literal reading of the plain language of the special mobile equipment statute does not render the sense dubious, and we have not been able to glean an intent on the part of the Legislature to have the words read in the conjunctive. As a result, we think that the plain language of the special mobile equipment statute mandates an interpretation by which a vehicle will be deemed special mobile equipment if it is not designed primarily for transportation of persons or property and is incidentally operated or moved over the highways, or if it is not used primarily for transportation of persons or property and is incidentally operated or moved over the highways. In other words, the vehicle must be (1) incidentally operated or moved over the highway and (2) not designed primarily for transportation of persons or property, or (3) not used primarily for transportation of persons or property; the presence of factor (1) along with the presence of either factor (2) or factor (3) will qualify a vehicle for the exemption. In the case at bar, the tanker-trailer was only incidentally moved over the highway, and was not used primarily for transportation. As a result, under the plain language of the statute, the tanker-trailer qualifies as special mobile equipment and is exempt from the registration requirements under MCL 257.216(d); MSA 9.1916(d).
The question we must now answer is whether Davidson should have an effect on this conclusion. It is the Supreme Court’s obligation to overrule or modify its case law, and until and unless the Supreme Court takes such action, this Court and all lower *52courts are bound by the Supreme Court’s authority. Boyd v W G Wade Shows, 443 Mich 515, 523; 505 NW2d 544 (1993). This Court may properly express its belief that a decision of the Supreme Court was wrongly decided, but that conclusion does not excuse this Court from applying the rule of law from that decision. Id. However, a question that is neither considered nor essential to the resolution of a case is dictum and does not establish a rule of law. People v Green, 205 Mich App 342, 346; 517 NW2d 782 (1994).
In our opinion, the language in Davidson relied upon by plaintiff was not essential to the resolution of Davidson and is therefore dictum and not binding upon us. The Supreme Court’s statement suggests that if a vehicle was either designed or used primarily for transportation, it does not qualify as special mobile equipment.2 However, the question whether a vehicle qualifies as special mobile equipment when that vehicle is either designed or used primarily for transportation was not at issue in Davidson because the vehicles in that case were designed and used as such. In other words, because the vehicles in Davidson were designed and used primarily for transportation, a determination whether the “or” in “not designed or used” is disjunctive or conjunctive was not essential to the resolution of the case. As a result, we dismiss the cited passage in Davidson as dictum and opt for applying the plain language of the statute.
In conclusion, because the tanker-trailer is not used primarily for transportation of persons or property *53and is incidentally moved over public highways, it is special mobile equipment and exempt from registration. Therefore, the tanker-trailer qualifies as “mobile equipment” and not an “automobile” under the policy at issue. As a result, the policy’s automobile exclusion does not apply and plaintiff has a duty to defend and indemnify.
Because of our disposition of plaintiff’s claim, we need not address defendant’s cross appeal.
Affirmed.
Hood, J., concurred.The Attorney General has adopted an interpretation of “special mobile equipment” that is based on the Supreme Court’s statements in Davidson. See OAG, 1960, No 3456, p 64 (April 4, 1960). However, Attorney General opinions are not precedentially binding on this Court. Chapman v Peoples Community Hosp Authority of Michigan, 139 Mich App 696, 702; 362 NW2d 755 (1984).
We agree with the Supreme Court that the presence of Davidson’s factor (3) alone will defeat the exemption; a vehicle must not be more than incidentally used on roads open to public travel. Therefore, our focus is on the use and design factors.