TOBRINER, J.

The plaintiffs, the wife and son of Arthur O. Dillenbeck, deceased, brought this action against the City of Los Angeles for the wrongful death of Dillenbeck arising out of a collision between his vehicle and a police car operated by Officer Abraham Weber in the course of his employment with the Los Angeles Police Department.

The accident in question occurred on January 22, 1962, at approximately 2 p.m., at the intersection of Wilshire Boulevard and Hobart Avenue, a business area in the City of Los Angeles. The decedent operated a 1961 Oldsmobile in a northerly direction on Hobart Avenue. Officer Weber, responding to a police radio broadcast ordering all units to proceed to the site of a suspected bank robbery, drove east on Wilshire Boulevard with both the red lights and the siren on his vehicle activated and operating. As a result of injuries sustained from the collision, Dillenbeck died on January 24, 1962.

Rain fell steadily at the time of the accident; the streets were wet. The windows of the Dillenbeck vehicle were closed; the windshield wipers were operating; the car radio was playing at a normal volume.

A number of witnesses testified that at the time of the accident the traffic control light at the intersection showed green for Dillenbeck and red for Weber. Officer Weber stated that he had not noticed the color of the traffic signal. The defense produced no evidence to the effect that the light was green for Weber.

Several eyewitnesses testifying for plaintiffs estimated Weber's speed at between 40 and 60 miles per hour. Weber stated, however, that he drove his vehicle, both through the intersections and otherwise, at a constant speed of 30 miles per hour. The city produced witnesses whose estimates agreed with the officer's statement. The posted speed limit on Wilshire is 35 miles per hour.

A large office building stands on the southwest corner of the intersection of Hobart and Wilshire. Officer Weber testified that this building, together with vehicles and pedestrians, partially obstructed his view of the southern portion of Hobart Avenue, from which decedent emerged.

The jury returned a verdict in favor of the city and against the plaintiffs by a 10 to 2 vote. After the entrance of judgment on the verdict and the denial of a motion for new trial, plaintiffs brought this appeal.

The sole dispute on appeal centers on the trial judge's refusal to allow plaintiffs to make use of either various "Daily Training Bulletins" (hereinafter bulletins) of the Los Angeles Police Department or of former Police Chief Parker's foreword to these bulletins explaining their general limitation to "those things which the officer must know, or should know, to be able to do a professional job." In particular, plaintiffs attempted to introduce into evidence bulletins Nos. 51, 52, 53, 54, 55, and 56, all of which set out how an officer should operate a motor vehicle under emergency conditions.

[1a] We shall explain why we have concluded that some of the proffered bulletins should have been admitted into evidence on the basis of the theories advanced by plaintiffs. In the first place, plaintiffs offered the bulletins as substantive proof that Weber, who allegedly did not comply with some of the instructions contained in the bulletins, drove negligently in colliding with decedent's car. In the second instance, in an effort to show that Weber acted carelessly, plaintiffs attempted to cross-examine Weber as to his knowledge of both instructions and factual statements in the bulletins, such as the effect of buildings, rain, and closed windows, that relate to audibility of the siren. Finally, addressing themselves to the question whether decedent was contributorily negligent in proceeding across Wilshire when Weber's siren was in operation, plaintiffs offered the bulletins into evidence as proof of facts tending to suggest that decedent might well not have heard the siren. The trial judge prohibited use of the bulletins on any of the three theories; we believe that in so ruling the court erred.

At the outset we note, as both parties apparently agree, that Torres v. City of Los Angeles (1962) 58 Cal.2d 35 [ 22 Cal.Rptr. 866, 372 P.2d 906], sets forth the standard of care governing the operation of emergency vehicles. In that case involving the collision of two fire trucks in the process of responding to an emergency alarm, we stated, in discussing the liability of the employer of a driver of an emergency vehicle in the light of the exemptions of Vehicle Code section 454 (now section 21055): "We can attribute to the legislative intent, in addition to the requirement of an adequate warning to others using the highway, the further requirement that the driver of an emergency vehicle exercise that degree of care which, under all the circumstances, would not impose upon others an unreasonable risk of harm. In short the statute exempts the employer of such a driver from liability for negligence attributable to his failure to comply with specified statutory provisions, but it does not in any manner purport to exempt the employer from liability due to negligence attributable to the driver's failure to maintain that standard of care imposed by the common law." (P. 47.)

In Torres we concluded: "[I]t is manifest that as to such conduct not specifically exempt from the imposition of liability, the degree of care lawfully imposed upon the agents or the employees of a municipality is that care consistent with the exercise of ordinary prudence in all the prevailing circumstances, including those circumstances manifest at the time of an emergency call. The question to be asked is what would a reasonable, prudent emergency driver do under all of the circumstances, including that of the emergency." (Italics added.) ( 58 Cal.2d 35, 51.) (See generally, Morrison, Negligent Operation of a Police Vehicle (1967) 16 Clev.-Mar.L.Rev. 442.)

The instant controversy thus does not turn on the controlling standard of care: the Torres case sets the standard. Rather, the present case involves the extent to which plaintiffs can utilize the directives and statements of facts in the police department's bulletins to assist the jury in applying the Torres standard.

1. The bulletins should have been admitted upon the grounds ( a) that they constituted evidence of the standard of due care applicable to the course of conduct of Officer Weber, and ( b) that the officer's failure to follow the safety rules promulgated by his employer constituted evidence of his negligence.

In the leading case of Powell v. Pacific Electric Ry. Co. (1950) 35 Cal.2d 40 [ 216 P.2d 448], an action for damages arising out of a collision at a railroad crossing, this court held that the trial court properly allowed into evidence a train-operating rule requiring motormen to reduce their speed "a sufficient distance in advance" of a highway crossing to allow the train "to coast on approach to crossing, to enable full braking power being obtained in emergencies."

In Powell we stated: "The rule was properly admitted in evidence as bearing on the standard of care respondent thought appropriate to insure the safety of others at its track crossings." (35 Cal.2d at p. 46; see also Beal v. Blumenfeld Theatres, Inc. (1960) 177 Cal.App.2d 192, 194 [ 2 Cal.Rptr. 110]; Davis v. Johnson (1954) 128 Cal.App.2d 466, 472 [ 275 P.2d 563]; cf. James Sigerson, Particularizing Standards of Conduct in Negligence Trials (1952) 5 Vand.L.Rev. 697, 710-712; 2 Wigmore, Evidence (3d ed. 1940) § 282; Witkin, Cal. Evidence (2d ed. 1966) pp. 483-484; Note (1956) 50 A.L.R.2d 16.) [2] The safety rules of an employer are thus admissible as evidence that due care requires the course of conduct prescribed in the rule. Such rules implicitly represent an informed judgment as to the feasibility of certain precautions without undue frustration of the goals of the particular enterprise. Accordingly, they may well be extremely useful to the trier of fact, who, applying the amorphous standard of "due care," must strike a fair balance between the reduction of the risk to the public and the assurance of an effective use of an emergency vehicle.

Introduced for the purpose of particularizing the standard of care, such safety rules theoretically constitute hearsay: an attempt to prove the truth of the matter implicitly asserted — that due care requires certain conduct. (Evid. Code, § 1200; cf. James Sigerson, Particularizing Standards of Conduct in Negligence Trials, supra, 5 Vand.L.Rev. 697, 712.) They are admissible, however, as an implied admission of a party opponent. (Evid. Code, § 1220; Herrera v. Southern Pac. Co. (1957) 155 Cal.App.2d 781, 788 [ 318 P.2d 784]; Witkin, Cal. Evidence, supra, pp. 483-484, and cases cited therein; cf. Smellie v. Southern Pac. Co. (1933) 128 Cal.App. 567, 583 [ 18 P.2d 97, 19 P.2d 982] (in denying a hearing, the Supreme Court withheld approval of the District Court of Appeal's rejection of an admissions theory).) [3a] Applying this well established legal doctrine of admissibility to the instant case, we conclude that the bulletins at issue contain at least two safety rules of the Los Angeles Police Department that relate to the instant factual situation and hence should have been introduced into evidence.

First, bulletin No. 53 states: "An officer is seldom, if ever, justified in travelling at a speed greater than the district speed. Certain circumstances might justify higher speeds; however, they must decidedly outweigh the additional hazard." Similarly, bulletin No. 55 reads, in part: "An officer is seldom justified in operating a vehicle under emergency conditions at a rate higher than district speed." Second, bulletin No. 54 states: "To reduce the possibility of conflict, an emergency vehicle proceeding against a traffic control device should decelerate to approximately fifteen m.p.h. through a blind intersection." Since plaintiffs introduced substantial evidence that Officer Weber violated both of these rules, the jury should have had the opportunity to consider them as evidence of the requirements for public safety necessary to meet the standard of due care in the operation of an emergency vehicle.

[4a] In opposing this conclusion, the city argues that the bulletins are only informative and instructive in nature, and hence not "rules" within the meaning of the doctrine that safety rules of an employer are evidence of the requirements of due care. This literal argument fails, however, on its own premises, for the word "rule" is a term of wide and varied significance, depending on the context (cf. City of Los Angeles v. Gager (1909) 10 Cal.App. 378, 380 [ 102 P. 17]), and in one sense carries the meaning "that which is prescribed or laid down as a guide to conduct" (77 C.J.S. 544). Certainly the bulletins in question satisfy at least this minimal standard.

Furthermore, arguments grounded solely in the semantics of the word "rule" do not furnish a sound benchmark for decision. In determining whether an employer's directive is a "safety rule" admissible as evidence of negligence, the issue turns on whether the directive in question affords a specific indication of the employer's reconciliation of the conflict between maximum efficiency in operations and maximum safety to the public. [3b] Since bulletins Nos. 53, 54, and 55, quoted supra, attempt to reach such a reconciliation, they are admissible.

[4b] The city also argues that, in defining "rule," the meaningful distinction must lie between detailed, unequivocal directives by the employer and discretionary guidelines to employees. This distinction, however, relates only to the nature of the subject matter: some conduct may be amenable to hard-and-fast treatment; other conduct, such as the operation of an emergency vehicle, may require discretionary consideration of a multitude of factors. In either event, the guideline, if it indicates with sufficient specificity the employer's reconciliation of the conflict between safety and efficiency, may constitute an "employer safety rule."

The cases have, indeed, held "discretionary rules" admissible as employer safety rules. In Powell v. Pacific Electric Ry. Co., supra, 35 Cal.2d 40, the rule at issue required the motorman to reduce speed a "sufficient" distance in advance of a highway crossing. In Davis v. Johnson, supra, 128 Cal.App.2d 466, the employer required that a trainman be stationed on the rear of the train "when practicable." Finally, in Torres v. City of Los Angeles, supra, 58 Cal.2d 35, a case which, as we have noted, involved fire department rules for emergency vehicles, similar rules to those here at issue were admitted into evidence and relied upon heavily. In all of these cases the question of admissibility turned on whether the directive served as a safety guideline by the employer, not on whether it allowed some discretion to the employee.

[3c] These rules are admissible, however, only as evidence of the component requirements of due care. As one factor in this determination their evidentiary effect depends entirely on their persuasiveness with the individual trier of fact. (E.g., Powell v. Pacific Electric Ry. Co., supra, 35 Cal.2d 40, 46.) This limitation allows ample opportunity for the employer to explain that he established a given rule, not as a reflection of his opinion as to what specific conduct comports with due care, but solely from an excess of caution. Alternatively, because due care is a highly fact-oriented standard, the employer might well argue that, because of the exigencies of the occasion, a safety rule is simply inapplicable. A rule that in many situations would compose a highly persuasive particularization of the requirements of due care might thus carry little or no weight with the jury or trial judge in a particular circumstance. [5] The safety rules in bulletins Nos. 51-56 are admissible, moreover, on a second, separate, non-hearsay theory that places no reliance on the employer's implicit resolution of the conflict between efficient operations and safety: they may be introduced on the ground that an employee's failure to follow a safety rule promulgated by his employer, regardless of its substance, serves as evidence of negligence. ( Simon v. City County of San Francisco (1947) 79 Cal.App.2d 590, 597 [ 180 P.2d 393]; Hartford Acc. Indem. Co. v. Bank of America (1963) 220 Cal.App.2d 545, 561 [ 34 Cal.Rptr. 23]; Gett v. Pacific Gas Electric Co. (1923) 192 Cal. 621, 625 [ 221 P. 376]; Southern Pac. Co. v. Haight (9th Cir. 1942) 126 F.2d 900, 909.) In short, the jury is entitled to conclude that the mere fact of violation of a safety rule promulgated by the employer is evidence that the employee conducted himself carelessly. In the instant case, the jury might well have concluded, if it believed the evidence presented by plaintiffs' witnesses, that Officer Weber negligently disobeyed the city's directives as to speed through intersections and speed in execess of the posted limits.

2. The court should have permitted, because of its potential relevance to the issue of negligence, the cross-examination of Officer Weber as to his knowledge of safety rules and factual matters contained in the bulletins in order to establish his training and current familiarity with such matters.

[6] Many of the cases cited above that have held that safety rules may be admitted as evidence of negligence have also upheld cross-examination of the employee on his knowledge of these rules (e.g., Simon v. City County of San Francisco, supra, 79 Cal.App.2d 590; Sapp v. W.T. Grant Co. (1959) 172 Cal.App.2d 89 [ 341 P.2d 826]; Torres v. City of Los Angeles, supra, 58 Cal.2d 35). Thus, the trial judge erred in refusing to allow the cross-examination of Officer Weber as to his knowledge of bulletins Nos. 51-56.

Moreover, a second rationale justified the cross-examination. Plaintiffs should have been permitted to show that Officer Weber, by reason of his extensive training and experience, possessed a superior knowledge both of the risks arising from use of a vehicle with a siren and of effective methods of minimizing these risks. If the cross-examination had elicited that Weber had knowledge of the departmental rules discussed supra and the facts contained in the bulletins, then the court should have given an instruction to the effect that the jury, in assessing liability, should measure Weber's conduct according to that of a reasonably prudent man possessing similar knowledge (Rest.2d Torts, § 289, subd. (b); see generally, Prosser, Law of Torts, supra, p. 164 and cases cited therein).

Alternatively, if Weber had indicated an ignorance of the rules or factual statements contained in the bulletins, this, too, might be evidence of negligence that the jury could properly consider. If the jury believed plaintiffs' witnesses, plaintiffs would then have shown not only that Weber did not follow an accepted rule but also that, despite Chief Parker's statement that the bulletins contained only that which an officer "should know . . . to be able to do a professional job," the officer was unaware of the relevant departmental rule.

3. The bulletins should have been admitted as evidence of decedent's lack of contributory negligence.

[7] At the trial the question whether decedent was contributorily negligent in proceeding across Wilshire Boulevard pivoted on whether a reasonably prudent person in decedent's position should have heard the siren and hence remained stationary even though the traffic signal favored him. The bulletins contained factual statements relative to whether a person in decedent's car on Hobart Avenue, with the windows closed and radio playing at a normal volume, could have heard the siren (see, e.g., fn. 8, supra). As implied admissions that composed factual statements by the city's experts on the operation and effect of sirens, the bulletins were admissible on such factual matters.

[1b] In sum, the issue before us does not turn upon whether the bulletins draw the correct lines for the proper conduct of the officers, or indeed, whether the statements of the bulletins are valid. The arguments against their viability may properly be urged to the jury. We pass upon, and uphold, only the admissibility of the bulletins, which thereafter may serve as the source of debate.

The trial court should also have permitted the cross-examination of Officer Weber as to his knowledge of safety rules and factual statements contained in the bulletins; these questions pertained to the officer's training and present familiarity with the subject matter of the bulletins. Since the evidence at trial was fairly evenly balanced and since plaintiffs adduced competent, credible proof that Officer Weber exceeded the speed limits and proceeded through intersections at a speed in excess of 15 miles per hour, it is reasonably probable that a result more favorable to plaintiffs would have been reached in the absence of the error. Accordingly, pursuant to People v. Watson (1956) 46 Cal.2d 818, 836 [ 299 P.2d 243], the error was prejudicial.

The judgment is reversed.

Traynor, C.J., Peters, J., Mosk, J., and Sullivan, J., concurred.