FELDMAN, Vice Chief Justice.
This petition for review asks that we reinstate the trial judge’s ruling forbidding discovery concerning seat belt use in a personal injury action. The basic question presented is whether Arizona should recognize the so-called “seat belt defense.” We granted review to determine this issue of statewide importance and to settle a conflict of authority between the divisions of our court of appeals. Rule 23, Ariz.R.Civ. App.P., 17B A.R.S.; Rule 8(b), Ariz.R.P. Spec.Act, 17B A.R.S. We have jurisdiction under Ariz. Const, art. 6, § 5(3) and A.R.S. § 12-120.24.
FACTUAL AND PROCEDURAL SUMMARY
On the evening of November 8, 1985, Cindy Law was driving her parents’ car in. Tempe, Arizona. She apparently pulled in front of an automobile operated by James Harder, who swerved violently to avoid a collision. Unfortunately, his evasive maneuver overturned the Harder vehicle. Harder and his wife were not wearing their seat belts and were thrown from their car —James through a closed sunroof. The Harders suffered severe orthopedic injuries as a result of the accident.
The Harders (plaintiffs) brought a negligence action against Cindy Law and her parents (defendants). During the course of discovery, defendants sought information concerning plaintiffs’ use and experience with seat belts and shoulder restraints. Plaintiffs objected to these discovery requests on the grounds that the subject was irrelevant under the holding of Nash v. Kamrath, 21 Ariz.App. 530, 521 P.2d 161 (1974). In that case, division two of our court of appeals held that evidence of a passenger’s failure to wear a seat belt was inadmissible either to show breach of a duty to minimize damages or to prove contributory negligence.
Defendants moved to compel discovery. In June 1986, the trial judge denied the motion and issued a protective order, concluding that under Nash motorists have no duty to wear seat belts. Thus, evidence of a causal connection between the failure to wear seat belts and the extent of plaintiffs’ injuries was irrelevant. Stymied at the trial level, defendants filed a special action petition1 with division one of the court of appeals, which granted jurisdiction.
The court of appeals vacated the trial judge’s protective order and held that evidence of seat belt nonuse was admissible so long as defendants could demonstrate a causal relationship between the nonuse and the injuries. Law v. Superior Court, 157 Ariz. 142, 755 P.2d 1130 (App.1986). The court concluded that under the interrelated doctrines of avoidable consequences and mitigation of damages, motorists were responsible to take reasonable pre-accident measures to prevent or reduce damages from foreseeable injury. Failure to avoid or mitigate foreseeable damages would result in a corresponding reduction in the damages awardable. The court found that the absence of a mandatory state seat belt law did not negate the duty to mitigate damages. Nor did the comparative negligence statute (A.R.S. § 12-2505) limit the jury’s power to reduce damages solely to cases of contributory negligence or assumption of the risk.
In their petition for review, plaintiffs ask us to resolve the conflict between this case and Nash. See Rule 23, Ariz.R.Civ.App.P., 17B A.R.S. Plaintiffs maintain that the Nash analysis is still valid and suggest several other reasons why this court should not sanction the introduction of evidence concerning seat belt nonuse as an aid to the apportionment of damages. Plaintiffs’ ulti[149]*149mate contentions may be summarized as follows:
1. Motorists need not assume that they face danger from the negligence of others;
2. Seat belts cause as many injuries as they prevent;
3. There is no duty to wear seat belts;
4. The entire matter should be left to the legislature;
5. The victim’s seat belt nonuse should not create a windfall for the tortfeasor;
6. The incorporation of evidence of seat belt nonuse would unduly complicate litigation;
7. Allowing the introduction of evidence on seat belt nonuse would initiate a series of unwanted and unforeseeable consequences for accident litigation in our state.
To resolve these issues, we must first examine the evolution of seat belt technology and its relationship to the law.
I. AN OVERVIEW OF THE SEAT BELT PROBLEM
A. The Seat Belt Defense
In late 1955, Ford and Chrysler first offered lap belts as optional equipment on their consumer automobiles.2 In 1968, Federal Motor Vehicle Safety Standard No. 2083 required automakers to install a lap belt for each occupant as well as a shoulder harness for the outboard front occupants on all automobiles made after January 1968. State and federal requirements for seat belt4 installation were a response to increasingly authoritative evidence that seat belts could prevent many deaths and injuries arising from automobile accidents.5
As seat belts became a standard automotive fixture, defendants increasingly raised the “seat belt defense.” At first, defense attorneys attempted to use the defense as a complete bar to recovery by showing that plaintiff was contributorily negligent.6 These efforts were generally unsuccessful.7 Courts were unwilling to totally deny recovery based on a finding of contributory negligence when it was almost certain in every case that nonuse of the seat belt was not a cause of the primary accident.8
The focus of defense efforts rapidly shifted to asserting that the victim had failed to properly mitigate damages by not wearing a seat belt.9 The mitigation theory sharply split the courts. Some jurisdictions accepted the idea that a plaintiff was responsible to take reasonable pre-accident safety measures.10 Most courts refused to bend traditional mitigation concepts to cover the victim’s pre-accident conduct.11 Arizona followed this majority rule in Nash, decided in 1974. From that point until the [150]*150present case, Arizona courts refused to allow defendants to use evidence of seat belt nonuse to prove either contributory negligence or failure to mitigate damages.
Nash was based upon a three-prong rationale. The first was that evidence of seat belt nonuse was irrelevant because it ran “counter to the traditional notion that, unless put on notice to the contrary, one has a right to assume that other persons upon the highway will not be negligent.” 21 ArizApp. at 532, 521 P.2d at 163, citing 2 F. HARPER & F. JAMES, THE LAW OF TORTS § 22.10 (1956). The court pointed out that a driver should have a reasonable expectation of safety on the highway and should not be required, therefore, to “truss himself up in every known safety apparatus” before driving. Id., citing Kleist, The Seat Belt Defense — An Exercise in Sophistry, 18 HASTINGS L.J. 613 (March 1967). Of course, Nash was decided at a time when Arizona courts followed contributory negligence — a theory now transformed to comparative negligence by A.R. S. § 12-2505(A), which became effective August 31, 1984 and applies to the case under consideration. See generally Butler & Gage, Comparative Negligence and Uniform Contribution: New Arizona Law, 20 ARIZ.B.J. 16 (June/July 1984).
The next basis for the Nash analysis was the concept that use of a seat belt might in itself present dangers to motorists. If that were true, the law could hardly hold non-use to be a violation of reasonable standards. As a corollary to the last mentioned principle, the court finally held there was no duty to fasten a seat belt, and failure to do so could not be considered a breach of any duty to minimize damages. 21 Ariz. App. at 532-33, 521 P.2d at 163-64.
We must now decide whether the Nash position should remain the proper rule for the state of Arizona. In our view, the technological and legal changes that have occurred in the twelve years that passed between Nash and the decision in the present case must determine which view of the law represents better policy. One of the most dramatic changes that has occurred in this period is the general acceptance of comparative negligence principles.
B. The Growth and Relevance of Comparative Negligence
The rapid acceptance of comparative negligence principles in the United States came just after many jurisdictions had initially determined to accept or reject the seat belt defense under either contributory negligence or mitigation of damages theories. In 1960, only six states had adopted comparative negligence.12 From 1965 to date, thirty-eight states have statutorily or judicially accepted comparative negligence.13 Apparently only six states and the District of Columbia still adhere to the full contributory negligence defense.14
Traditional contributory negligence theory, of course, militates for rejection of the seat belt defense. Contributory negligence is conceptualized in terms of conduct by plaintiff which contributed to the occurrence of the accident. See McDowell v. Davis, 104 Ariz. 69, 72, 448 P.2d 869, 872 (1968). Because seat belt nonuse seldom contributes to the occurrence of the accident, it does not easily fit into the theory of contributory negligence. But see Kington v. Camden, 19 Ariz.App. 361, 507 P.2d 700 (1973) (if driver had fastened her seat belt, she would not have lost control of her vehicle and caused crash).
Further, if the seat belt defense is considered a form of contributory negligence, it would totally bar recovery. Theoretically, that was the situation under the former Arizona law. McDowell, supra. However, nonuse of a seat belt rarely causes all of plaintiffs injuries. In the typical accident, nonuse simply increases the number or severity of injuries beyond those which would have occurred had the plaintiff used a seat belt. Thus, under traditional contributory [151]*151negligence principles, the seat belt defense would have constituted a harsh and untenable policy denying all recovery to nonusers, despite the lack of any causal nexus between seat belt nonuse and some of the injuries.
Comparative negligence theories eliminate most of those problems because an adverse finding on nonuse does not bar recovery but merely reduces the damages in proportion to the contributing factor of seat belt nonuse. Thus, since Nash, courts originally unwilling to enforce a total bar to plaintiffs recovery under contributory negligence now are able to make a proportionate reduction of damages under comparative negligence concepts.15 This, in fact, furthers the basic goal of comparative negligence theory — to allow an appraisal of all relevant facts in determining the correct damages to be given each claimant in a personal injury case.16 •
Given this choice, courts able to apply comparative negligence principles to seat belt defense cases broke their analysis into at least two steps. Nonuse of the seat belt generally was not a factor contributing to the accident. However, by failing to use available seat belts, the plaintiff might have enhanced the injuries over those which would have occurred if the belts had been used.17 Thus, to ascertain the proper damages, the emphasis switched to this “second collision” between the occupants and their environment.18 Even with this new focus, the difficulty of determining the complex calculus of all conceivable causal connections involved in any accident dissuaded some courts from recognizing the defense.19 Nevertheless, the rise of comparative negligence undermined much of the theoretical basis for rejection of the defense. At the same time, the law was beginning to catch up with technology.
C. Legislation Requiring Seat Belt Installation and Use
Most seat belt systems are not “passive”; the user must “buckle up.” As the years passed following the start of widespread seat belt installation, designers and engineers devised safety restraint systems that were entirely passive.20 It is now possible to equip automobiles with' automatic harness or air bag systems that do not need to be manually activated.21 Because of the expense of these devices, manufacturers have strenuously objected to installing them as standard equipment22 Faced with overwhelming evidence that passive restraint systems would save many lives and prevent countless injuries, in 1984 the National Highway Traffic Safety Administration adopted changes to Federal Motor Vehicle Safety Standard No. 208 requiring the installation of passive restraints in all new cars starting with model year 1990, unless states containing at least two-thirds of the nation’s population enact mandatory seat belt use statutes before the regulation’s [152]*152effective date.23 The federal standard also requires that conforming state statutes contain provisions specifying that violation of the seat belt law may be used to mitigate damages in any post-accident civil litigation and that nonuse will result in a criminal penalty of at least twenty-five dollars.24
Prior to the promulgation of the new federal rule, no state had enacted a law requiring motorists to use seat belts.25 It now appears that over twenty states have enacted at least some form of such legislation.26 It remains to be seen whether these new laws will meet the federal requirements and whether courts will use them to impose a statutory “duty” to wear seat belts for purposes of establishing fault and assessing damages in tort litigation. Arizona has not yet passed any general legislation mandating seat belt use. But see A.R.S. § 28-907 requiring seat belt use for children four years old or younger.
II. THE SEAT BELT DEFENSE IN ARIZONA
With the foregoing in mind, we must now decide whether Arizona will adopt some version of the so-called seat belt defense. To do so, we first examine the current validity of the principles underlying the Nash decision.
A. The Probability of Motor Vehicle Accidents
Because Nash held that motorists could assume that all who use the highways will drive with care, the decision imposed no duty to anticipate injury. Over a lifetime, however, it is almost certain that a motor vehicle accident will injure the average motorist.27 The clear foreseeability of automobile accidents is the reason most courts now hold automobile manufacturers responsible to make vehicles capable of providing a reasonable level of protection to automobile occupants. See, e.g., Larsen v. General Motors Corp., 391 F.2d 495 (8th Cir.1968) (original case adopting crashworthiness doctrine). Our court of appeals recently applied this theory to the design of motorcycles. Cota v. Harley Davidson, A Division of AMF, Inc., 141 Ariz. 7, 12-14, 684 P.2d 888, 893-95 (App.1984).
Given modern-day conditions, we conclude as a matter of public policy that the law must recognize the responsibility of every person to anticipate and take reasonable measures to guard against the danger of motor vehicle accidents that are not only foreseeable but virtually certain to occur sooner or later. Rejection of the seat belt defense can no longer be based on the antediluvian doctrine that one need not anticipate the negligence of others. There is nothing to anticipate; the negligence of motorists is omnipresent.
B. Seat Belts as a Cause of Harm
In Nash, the court noted that seat belts may actually create or enhance injuries instead of preventing them. 21 Ariz.App. at 532, 521 P.2d at 163. There are reports of tragic situations when wearing a seat belt may trap a vehicle occupant in a burning, sinking, or disabled automobile.28 Such cases are noteworthy precisely because they are so rare.29 It is statistically far [153]*153safer for motorists to remain in their vehicles than to suffer the vagaries of a violent ejection from the automobile.30 There are also claims that properly worn seat belts can cause direct and serious harm to users. These assertions focus on abdominal and spinal injuries that may be attributable to seat belt use. However, it is also true that in almost every instance seat belt-induced injuries are far less drastic than those that would have been incurred without the seat belt use.31 As a general rule, a motorist is simply better off wearing a seat belt.32 We conclude from the technological data that continued nonrecognition of the seat belt defense cannot be based on the general concept that seat belts cause harm. The opposite is generally true.
C. The “Duty” to Wear Seat Belts
Nash held there was no duty to wear seat belts. We acknowledge that “duty” to use restraints is generally considered the prime question in cases such as this. See, e.g., Clarkson v. Wright, 108 Ill.2d 129, 90 Ill.Dec. 950, 483 N.E.2d 268 (1985) (a decision relied upon by the trial court in the present action). Whatever its relevance to the Nash analysis, however, we do not believe that duty in its usual formulation remains a relevant component of the seat belt defense analysis. “Duty” is normally defined in terms of the obligation of care owed to one’s neighbors. Markowitz v. Arizona Parks Board, 146 Ariz. 352, 706 P.2d 364 (1985). The problem, of course, is to determine who is a “neighbor.” W. PROSSER & W. KEETON, THE LAW OF TORTS § 75, at 535 (5th ed. 1984). Because in all but the rarest situation nonuse
ASSESSMENT REPORT IN THE NATIONAL SAFETY BELT USAGE PROGRAM (Sept. 1983).
of a seat belt presents no forseeable danger to others, it is probably incorrect to conceptualize the seat belt defense in terms of duty.
More importantly, evaluating seat belt nonuse under the rubric of duty fundamentally confuses that concept with the evaluation of the conduct that may or may not fulfill it. Duty is the “obligation, recognized by law, which requires [an actor] to conform to a particular standard of conduct in order to protect others against unreasonable risk of harm.” Markowitz, 146 Ariz. at 354, 706 P.2d at 366, citing Ontiveros v. Borak, 136 Ariz. 500, 667 P.2d 200 (1983). As indicated in Markowitz, we do not believe the concept of duty should be confused “with specific details of conduct.” 146 Ariz. at 355, 706 P.2d at 367, citing Coburn v. City of Tucson, 143 Ariz. 50, 52, 691 P.2d 1078, 1080 (1984).
Everyone has a “duty” to use due care to prevent injury to others. Nonuse of a seat belt is not a question of duty but rather a matter of conduct which only occasionally impinges on others.33 Thus, we believe that injuries sustained by the plaintiff as a result of his nonuse of an available seat belt are not so much a failure to use care to avoid endangering others but part of the related obligation to conduct oneself.reasonably to minimize damages and avoid foreseeable harm to oneself. Markowitz, supra; Coburn, supra.
Thus, the seat belt defense would ordinarily raise issues concerning the doctrine of avoidable consequences — a theory that denies recovery for those injuries plaintiff could reasonably have avoided. W. PROS-[154]*154SER & W. KEETON, supra, at 458, Plaintiffs argue that this doctrine is applied only to post-accident conduct and is inapplicable to events preceding the accident — -a time when plaintiffs supposedly had a right to assume that others would not act negligently.34 Assuming this is ordinarily true, we believe the common law conceptualization of the doctrine of avoidable consequences has been modified by our comparative negligence statute, which applies that doctrine to pre-accident conduct.
D. The Comparative Negligence Statute
When the Arizona legislature enacted the Uniform Contribution Among Tortfeasors Act in 1984, it added several important provisions to the model law delineated in 12 U.L.A. 63-107 (1975). These new sections constituted the statutory adoption of comparative negligence for our state. A.R.S. §§ 12-2505 to -2509. In any given case, the relevance of comparative negligence principles is normally a question for the jury. Cheney v. Superior Court, 144 Ariz. 446, 698 P.2d 691 (1985). If the jury does apply comparative negligence standards, the plaintiffs action is not barred, “but the full damages shall be reduced in proportion to the relative degree of fault which is a proximate cause of the injury or death, if any.” A.R.S. § 12-2505(A) (emphasis added).
The essential question is whether a plaintiff who does not wear an automobile seat belt is at “fault” for injuries enhanced or caused by the failure to use the seat belt. Neither the Arizona comparative negligence statute nor its progenitor uniform law contains any definition of “fault.” We do note the instructive definition of this term given in § 1(b) of the Uniform Comparative Fault Act (UCFA), 12 U.L.A. 39-40 (Cum.Supp.1987).
“Fault” includes acts or omissions that are in any measure negligent or reckless toward the person or property of the actor or others, or that subject a person to strict tort liability. The term also includes ... unreasonable failure to avoid an injury or to mitigate damages. Legal requirements of causal relation apply both to fault as the basis for liability and to contributory fault.
(Emphasis added.) As stated in the- official comment to the UCFA, negligent failure to use a seat belt would reduce damages solely for those injuries directly attributable to the lack of seat belt restraint. Id. Thus, as far as the calculation of damages is concerned, the comparative negligence statutes apply the doctrine of avoidable consequences to pre-accident conduct.
We are further guided in our determination of the fault issue by a series of well-reasoned seat belt cases from other comparative negligence jurisdictions. The first case is Insurance Company of North America v. Pasakarnis, 451 So.2d 447 (Fla.1984), quashing 425 So.2d 1141 (Fla.Dist.Ct.App.1982). In that case, defendant sought to reduce the overall damages by introducing evidence of plaintiffs nonuse of a seat belt. The Florida Supreme Court concluded that the obvious importance of the seat belt as a safety precaution made its nonuse a pertinent factor for the jury to evaluate. The court properly refused to base its analysis on concepts of duty and focused instead on the plaintiffs conduct:
Nonuse of the seat belt may or may not amount to a failure to use reasonable care on the part of the plaintiff. Whether it does depends on the particular circumstances of the case. Defendant has the burden of pleading and proving that the plaintiff did not use an available and operational seat belt, that the plaintiffs failure to use the seat belt was unreasonable under the circumstances, and that there was a causal relationship between the injuries sustained by the plaintiff and plaintiff’s failure to buckle up. If there is competent evidence to prove that the failure to use an available and operational seat belt produced or contributed substantially to producing at least a portion of plaintiffs damages, then the jury should be permitted to consider this [155]*155factor, along with all other facts in evidence, in deciding whether the damages for which defendant may otherwise be liable should be reduced. Nonuse of an available seat belt, however, should not be considered by the triers of fact in resolving the issue of liability unless it has been alleged and proved that such nonuse was a proximate cause of the accident.
451 So.2d at 454.
In Smith v. Goodyear Tire & Rubber Co., 600 F.Supp. 1561 (D.Vt.1985), the court responded as follows to assertions that it was improperly imposing a “duty” to wear seat belts:
We are unpersuaded by such reasoning. First, admitting such evidence would not create a duty but would merely allow the jury to consider the information on the question of negligence. Second, the test of negligence would continue to be whether the person acted reasonably under the circumstances presented. The jury’s discretion and common sense will remain as a check upon parties that might seek to make wild assertions of negligence. We do not presume to decide whether or not Plaintiff’s failure to fasten his seat belt in the instant case was reasonable. We do believe, however, that the arguments on both sides of the issue are such that a reasonable jury could decide either way.
600 F.Supp. at 1564 (first emphasis added; second emphasis in original).
Finally, in Lowe v. Estate Motors, Ltd., 428 Mich. 439, 410 N.W.2d 706 (1987), the Michigan Supreme Court considered the nonuse of seat belts as comparative negligence in an automobile products liability lawsuit. The Michigan Supreme Court also held that the duty issue was not the central problem. Id. at 461, 410 N.W.2d at 715. The court reinstated the trial judge’s denial of the plaintiff’s exclusionary motions. Id. at 475, 410 N.W.2d at 721. See also Hutchins v. Schwartz, 724 P.2d 1194, 1199 (Alaska 1986) (nonuse of seat belts is a relevant factor in apportioning damages in a state that has adopted comparative negligence by judicial decision).
Our examination of the applicable case-law and our analysis of the concept of “duty” lead us to the conclusion that the seat belt defense is not a question of duty at all. We reject those cases, such as Clarkson, supra, that rely on the absence of “duty” to reject the seat belt defense. We also disapprove the Nash analysis. At least under the comparative fault statute, each person is under an obligation to act reasonably to minimize foreseeable injuries and damages. Thus, if a person chooses not to use an available, simple safety device, that person may be at “fault.”
E. Preempting the Role of the Legislature
Plaintiffs claim that recognition of the seat belt defense is a matter we should leave to the legislature. The Arizona legislature has not passed any law mandating the use of seat belts except A.R.S. § 28-907, which basically requires the use of restraint systems only for children under four years of age. The child restraint law specifically precludes admission of evidence of nonuse in civil proceedings. A.R. S. § 28-907(H). Of course, young children could hardly be held at “fault” for failure to buckle up; with or without the statutory provision, we could not diminish a civil recovery for an infant whose parent, guardian, or custodian failed to place the child in a proper restraint system. See Town of Flagstaff v. Gomez, 23 Ariz. 184, 202 P. 401 (1921). Thus, we do not infer from this specific prohibition dealing with infants a general legislative intent to forbid the introduction of evidence that an adult motorist unreasonably failed to use a seat belt and enhanced his own injuries. Allowing the jury to assess damages by considering an adult’s failure to use seat belts does not conflict with the seat belt statute and does conform to our statutory comparative negligence scheme. We are furthering the statutory objectives in this area, not contradicting them.
Some courts hold that creation of a “seat belt defense” is solely a matter for legislative action. See, e.g., Thomas v. Henson, 102 N.M. 326, 695 P.2d 476 (1985), rev’g 102 [156]*156N.M. 417, 696 P.2d 1010 (App.1984); Fields v. Volkswagen of America, Inc., 555 P.2d 48, 62 (Okla.1976). We believe, however, that this court has an obligation to participate in the evolution of tort law so that it may reflect societal and technological changes. Summerfield v. Superior Court, 144 Ariz. 467, 698 P.2d 712 (1985). In some cases, this responsibility has compelled us to recognize duties that further public policy and legislative objectives, even though the specifics have not been enacted by the legislature. See, e.g., On-tiveros, supra.
Acceptance of the seat belt defense does not require us to violate the proper deference owed the legislature. We neither carry a legislative enactment past the intent which existed at the time of its passage nor recognize an obligation not already reflected in the lives of our citizens. We only acknowledge reality: the use or nonuse of a seat belt is an everyday matter of conduct which plays a significant role in determining the extent of injuries. To hold that we cannot let a jury consider such conduct on the issue of damages is to judicially transmogrify legislative nonaction on a common law damage issue into legislative intent to approve nonuse of seat belts. Such a conclusion has never been expressed by the legislature and is very far from the demonstrated legislative objectives in this area. Of course, if we are wrong, and if the legislature intends that in this state one may unreasonably refuse to use a seat belt and nevertheless hold another responsible for the resulting damages, it can easily enact such a policy.
F. Windfall to the Tortfeasor
Plaintiffs claim that by recognizing the seat belt defense, we would confer a windfall on tortfeasors. As noted ante, the crux of comparative negligence is a proper apportionment of damages based upon the fault of the respective parties. If a victim unreasonably failed to use an available, simple prophylactic device, then he will not be able to recover for damages created or enhanced by the nonuse.35 Thus, although some tortfeasors may pay less than they otherwise would, they will not pay less than they should. We do not believe this rule creates a windfall to the tortfeasor; it is an unavoidable consequence of our comparative negligence system.
G. Undue Complication of Litigation
Petitioners maintain that allowing apportionment of damages based on failure to use seat belts will unnecessarily complicate and protract litigation. The defendant must establish several factual predicates before seat belt nonuse may be presented to the jury. See Pasakarnis, supra. To prove these factors, the defendant may utilize qualified experts in the medical, scientific, and accident reconstruction fields. It is then up to the factfinder to evaluate the evidence and quantify the results under comparative negligence principles.
Of course, this process will take time and create new issues for the jury to decide. These problems are hardly insurmountable. Juries perform this type of operation on a regular basis in many types of civil and criminal cases. The very idea of comparative negligence requires that juries apportion fault. The same is true when juries apportion fault between joint tortfeasors. See A.R.S. § 12-2506 (apportionment of fault under comparative negligence and contribution statute). In some second impact or so-called “crashworthiness” cases, juries are required to determine the injuries attributable both to the original accident and to a manufacturer’s failure to produce an automobile capable of withstanding foreseeable accidents. See discussion in General Motors Corp. v. Edwards, 482 So.2d 1176, 1189 (Ala.1985). Courts [157]*157almost universally entertain such actions, even though some recognize the complications produced by injury apportionment. Id.
There is no doubt that the seat belt defense will complicate and lengthen litigation in some cases. While this certainly does not militate in favor of its acceptance, we believe the problem is no different in principle from that posed by any legal, technological or scientific advance. Neither law nor. society can ignore technological change simply because it makes decision more complex.
H. Unwanted and Unforeseen Consequences
As the final argument, plaintiffs assert that introducing evidence of seat belt non-use would propel our courts into a morass of unforeseen consequences. If seat belt nonuse is relevant, why not introduce evidence of failure to install air bags? Why not hold the plaintiff responsible for failure to buy a large car which is normally much safer in a crash than a small car?
We are faced with a concrete application of comparative negligence principles. We deal in this case only with a plaintiffs use or nonuse of a common, simple safety device available in his or her car. In making use of an available seat belt, a motorist need not possess engineering expertise, suffer significant inconvenience, install special equipment or purchase a different vehicle. He or she need use only a few seconds to fasten a convenient safety device. The exact bounds of fault in other fact situations is a matter for the common law to address in its customary evolutionary fashion. Ontiveros, 136 Ariz. at 504, 667 P.2d at 204.
I. Resolution
We conclude that irrespective of a duty to avoid injuring others, under the theory of comparative “fault,” nonuse of a seat belt is a factor that the jury may consider and use to reduce damages under the following conditions:
1. Where the date of the injury is after the effective date of the comparative negligence statute.
2. Where the injured party is of an age and discretion that his or her nonuse could be considered as “fault.”
3. When the nonuse was unreasonable under all of the circumstances. Of course, art. 18, § 5 of our Constitution protects the jury’s right to determine whether nonuse of a safety restraint is negligent and, if so, the consequences of that negligence. Hall v. A.N.R. Freight System, Inc., 149 Ariz. 130, 133-37, 717 P.2d 434, 437-41 (1986).
4. Where nonuse either causes injuries which would not have occurred had the restraint been used or enhances those injuries that did occur.
5. Where the evidence shows with reasonable probability the degree of enhancement.
The burden of establishing these matters, as with other matters of comparative negligence, is upon the defendant. See, e.g., Dura Corporation v. Harned, 703 P.2d 396, 404 (Alaska 1985). Further, the jury must be clearly instructed that nonuse of a seat belt is an issue bearing upon the extent of damages that may be recovered and not on any other issue.
CONCLUSION
Within the analytical framework of this opinion, we recognize the seat belt defense as a matter which the jury may consider in apportioning damages due to the “fault” of the plaintiff. Accordingly, in appropriate cases discovery will be available on the issue of nonuse.
We approve the portions of the opinion by the court of appeals that conform to this opinion. This case is remanded to the trial court for further proceedings consistent with our holding.
GORDON, C.J., and CAMERON, J„ concur.
MOELLER, J., did not participate in the determination of this matter.