delivered the Opinion of the Court.
The Colorado Governmental Immunity Act (GIA) waives the defense of sovereign or governmental immunity
1
for the op
*225
eration of a publicly owned or leased motor vehicle by a public employee. § 24-10-106(l)(a), 10A C.R.S. (1988). We granted certiorari to review
Bertrand v. Board of County Commissioners,
I
As this ease requires us to interpret one of the exceptions to the GIA, we believe it is appropriate first to resolve an inconsistency that has arisen in our opinions regarding the GIA. Specifically, we have stated that the immunity created by the GIA is in derogation of the common law and must be strictly construed,
State v. Moldovan,
Though the origin of sovereign immunity is obscure, the doctrine, as we know it, developed in England and was based upon the historical fiction that the king could do no wrong, and thus, was free from legal accountability.
See generally,
Edwin M. Borehard,
Governmental Responsibility in Tort,
36 Yale L.J. 1 (1926). The doctrine of sovereign immunity became deeply embedded in the English common law and subsequently, through judicial recognition and reiteration, became a familiar axiom in American jurisprudence.
2
See Kawananakoa v. Polyblank,
In
County Commissioners v. Bish,
In 1971, however, this court decided a trilogy of cases that fundamentally altered the common law of Colorado regarding the doctrine of sovereign immunity.
Evans,
[t]he effect of this opinion and its two contemporaries is simply to undo what this court has done and leave the situation where it should have been at the beginning, or at least should be now: in the hands of the General Assembly of the State of Colorado. If the General Assembly wishes to restore sovereign immunity and governmental immunity in whole or in part, it has the authority to do so.
Evans,
174 Colo, at 105,
In response to the Evans trilogy, the legislature passed the GIA. See Ch. 323, sec. 1, §§ 130-11-1 to -17, 1971 Colo.Sess.Laws 1204, 1204-11. The GIA legislatively restored the doctrine of sovereign and governmental immunity and also carved out a limited number of exceptions waiving immunity for various governmental acts. Ch. 323, sec. 1, § 130-11-6(1), 1971 Colo.Sess.Laws 1204, 1206.
With this brief history in mind, we can now remedy the inconsistency that has arisen in our opinions regarding the relationship between the GIA and the common law. The first case stating that the GIA is in derogation of the common law is
Stephen v. City & County of Denver,
The Colorado Governmental Immunity Act was a response to three Colorado Supreme Court decisions that prospectively overruled prior decisions recognizing a defense of governmental immunity in tort actions .... These decisions held that the legislature had authority to restore the doctrine in whole or in part. Thus, the Colorado Governmental Immunity Act is in derogation of the common law, and the legislative grants of immunity must be strictly construed.
Id.
(citations omitted). The
Stephen
court correctly recognized that
Evans
created a new common law in which the doctrine of immunity no longer existed and that the GIA was enacted in derogation of the holding in
Evans. See also State v. Moldovan,
In sum, the doctrine of sovereign and governmental immunity was part of the common law of Colorado until 1971 when this court abrogated the doctrine in the Evans trilogy. Thereafter, the legislature restored the doctrine and authorized a limited number of exceptions. Thus, it is apparent that the immunity created by the GIA is in derogation of the common law established in the Evans trilogy and must be strictly construed. See 3 Norman J. Singer, Sutherland Statutory Construction § 61.01 (5th ed. 1992) (discussing strict construction of statutes in derogation of the common law). To the extent that Bloomer and Jenks differ with this opinion, they are overruled.
II
We turn now to the facts of this case and the interpretation of the motor vehicle exception to the GIA. On the morning of June 26, 1989, an employee of the Board of County Commissioners of Park County (Board) was operating a road grader on a highway near Guanella Pass in Park County, Colorado. That same morning, Cheryl Bertrand (Bertrand), her children and a friend, were riding horses on a path adjacent to Guanella Pass Road in Park County. The horses were spooked by the noise of the road grader as it passed by the group, and as a result, Bertrand was thrown from her horse and was injured. Subsequently, she filed a complaint against the Board, claiming that the road grader was being negligently operated at an excessive speed, which caused her horse to bolt, and consequently, caused her accident. The Board asserted governmental immunity as an affirmative defense. Thereafter, the Board moved for judgment on the pleadings, arguing that a road grader is not a “motor vehicle” within the motor vehicle exception to immunity,
see
§ 24-10-106(l)(a), and that Bertrand’s claim is barred by the GIA. The trial court agreed and dismissed the complaint. Relying on
Bain v. Town of Avon,
A
The GIA bars any claim against a public entity for injuries that lie in tort or could lie in tort. § 24-10-108, 10A C.R.S. (1988 & 1993 Supp.). Nonetheless, there are a limited number of situations in which the legislature deemed it appropriate to waive the defense of sovereign immunity. See § 24-10-106(l)(a)-(f), 10A C.R.S. (1988 & 1993 Supp.). One such situation involves the operation of motor vehicles. This exception provides:
Sovereign immunity is waived by a public entity in an action for injuries resulting from:
(a) The operation of a motor vehicle, owned or leased by such public entity, by a public employee while in the course of his employment, except emergency vehicles operating within the provisions of section 42-4-106(2) and (3), C.R.S.
§ 24-10-106(l)(a).
The GIA does not define the term “motor vehicle,” nor has this court interpreted that term. The court of appeals, however, has done so. In
Bain v. Town of Avon,
The Board argues that we should apply the definition of “motor vehicle” contained in the Uniform Motor Vehicle Law as did the court of appeals in
Bain.
While the approach taken by the court of appeals is not unreasonable, the interpretation of one statute by reference to an unrelated statute is an unreliable means of ascertaining legislative intent. 2B Norman J. Singer,
Sutherland, Statutory Construction
§ 53.05, at 238 (5th ed. 1992);
see also Anderson v. Janovich,
B
In interpreting the motor vehicle exception, we are guided by accepted principles of statutory construction. Our primary goal is to determine and give effect to the intent of the legislature.
Jones v. Cox,
Though the term “motor vehicle” is not defined in the GIA, it is certainly a term of ordinary and common usage. Thus, we do not think it necessary to adopt a strained and complex definition which would require a trial court to examine the various characteristics of different types of government vehicles to determine if the vehicle in question is a *229 “motor vehicle” for purposes of section 24-10-106(l)(a). Rather, we believe it is fair to assume that the legislature intended the plain and ordinary meaning of “motor vehicle” to attach to that term as it appears in the GIA. Thus, for purposes of the GIA, we believe that a “motor vehicle” includes any “vehicle on wheels having its own motor and not running on rails or tracks, for use on streets or highways.” Webster’s Neiu World Dictionary of the American Language 930 (2d College ed. 1974).
We believe this construction is compatible with, and supported by, our prior conclusion that the GIA, being in derogation of the common law, is to be strictly construed.
See, e.g., State v. Moldovan,
Accordingly, we reverse the decision of the court of appeals and remand with directions to return the ease to the trial court for further proceedings consistent with this opinion.
Notes
. The term "sovereign immunity” generally refers to the immunity of the state or federal government whereas the term "governmental immunity" refers to the immunity of all levels of gov *225 ernment. See W. Keeton, D. Dobbs, R. Keeton & D. Owen, Prosser and Keeton on the Law of Torts, § 131, at 1033 (5th ed. 1984).
. Sovereign immunity in the United States has been justified by an explanation offered by Justice Holmes. "A sovereign is exempt from suit, not because of any formal conception or obsolete theory, but on the logical and practical ground that there can be no legal right as against the authority that makes the law in which that right depends."
Kawananakoa v. Polyblank,
. We recognize that some exceptions to the doctrine of immunity were created both legislatively,
see
1963 C.R.S. § 36 — 1—l(l)(b), and judicially,
see Boxberger v. State Highway Dept.,
. Though not mentioned in any of the early cases espousing the doctrine of sovereign immunity, it is true that as early as 1868, there was legislation stating that ”[t]he common-law of England, so far as the same is applicable and of a general nature, ... shall be the rule of decision, and shall be considered as of full force until repealed by legislative authority.” 1868 Revised Statutes of Colorado, ch. 16, sec. 1. This statute strengthens the proposition that the common law of Colorado incorporated the English common law doctrine of sovereign immunity.
. The common law is the body of law that develops through judicial decisions and, though generally followed as
stare decisis,
may be changed to comport with changing social attitudes as well as to avoid injustice.
See Funk v. United States,
.The fact that the ruling was prospective does not alter the fact that as of the date of the Evans trilogy, the common law with respect to sovereign immunity was changed. To further demonstrate that fact, it is significant to note that the parties in Evans, Flournoy and Proffitt were subject to the holding in the Evans trilogy.
. The Bain court briefly discussed the sparse legislative history of § 24-10-106(l)(a). What history exists is contained in the Legislative Council Report to the Colorado General Assembly, Governmental Liability in Colorado, Research Publication No. 134 (1968). The section discussing the waiver of immunity for the operation of motor vehicles states, "[t]he committee agreed that, with respect to injuries arising from automobile accidents caused by the negligent operation of government-owned motor vehicles, the defense of sovereign immunity should not be available to a public entity.” Id. at 136. In addition, in the Committee Recommendations, the paragraph discussing the waiver of immunity for government owned motor vehicles is captioned "automobile accidents.” Id. at xxi. However, the words "automobile” and "motor vehicle” are both used in the report. In addition, the legislation, as enacted, makes no reference to the word "automobile." Thus, the legislative history is not helpful in construing the term "motor vehicle.”
