OPINION OF THE COURT
ALDISERT, Circuit Judge.The major question presented by this appeal from a judgment for the plaintiff in a diversity case arising from a fatal traffic accident is whether the district court erred or abused its discretion by excluding evidence of the decedent’s blood alcohol level. In light of the Pennsylvania decisional law regarding admissibility of evidence of intoxication and the evidentiary support for the district court’s factual inferences, we conclude that the exclusion was neither error nor an abuse of discretion. Therefore, we affirm the judgment of the district court.
I.
Marshall Rovegno was killed when an overtaking truck owned by defendant Geppert Brothers, Inc., and driven by its employee, defendant Lewis J. Ward, collided with his truck, causing it to overturn. Invoking the district court’s diversity jurisdiction, Rovegno’s widow brought this wrongful death and survival action under Pennsylvania law. The trial produced conflicting testimony about the drivers’ actions immediately before the collision: plaintiff produced evidence tending to show that Ward misjudged the distance between his truck and the Rovegno truck in front of him and started his move into the passing lane too late; defendant Ward testified that he had pulled his truck fully into the passing lane and that Rovegno’s truck moved sideways into it. Testimony was also presented by a state trooper who reconstructed the accident from statements Ward and a witness gave to him at the scene and from skid marks that showed the point of impact to be in the left lane. His reconstruction placed the Rovegno truck partly in the left lane.
Defendants sought to introduce evidence that, as determined from a blood sample taken by the coroner, Rovegno’s blood alcohol level at the time of the accident was 0.158 percent. If permitted, defendants’ expert would have testified that a blood alcohol level of that degree would have made Rovegno unfit to drive. Concerned about the potential prejudicial effect of this evidence, the district court refused to admit it because it was not accompanied by other evidence, such as “excessive speed, recklessness or erratic driving.” Mem. op. at 3, reprinted in app. at 193. The jury, instructed by the court on comparative negligence, determined liability on the part of *329defendants to be 70 percent.1 The district court subsequently denied defendants’ motions for judgment n. o. v. or a new trial on liability. On appeal, defendants repeat their contentions that the trial judge should have given more recognition to the scientific nature of the proffered evidence of intoxication and also that the probative value of the blood alcohol level evidence outweighed its potential for prejudice because there was accompanying evidence that Rovegno’s driving was careless.2
II.
The scope of this court’s review of a trial judge’s decision to admit or exclude evidence of drinking or intoxication is a review for abuse of discretion. The exercise of discretion at issue in this appeal also implicates Pennsylvania law, however, and our review of the legal component of the lower court’s exercise of discretion is plenary. See Universal Minerals, Inc. v. C. A. Hughes & Co., 669 F.2d 98, 103 (3d Cir. 1981).
The relevant Pennsylvania decisional law springs from Fisher v. Dye, 386 Pa. 141, 148, 125 A.2d 472, 476 (1956):
[Wjhile proof of intoxication is relevant where reckless or careless driving of an automobile is the matter at issue, the mere fact of drinking intoxicating liquor is not admissible, being unfairly prejudicial, unless it reasonably establishes a degree of intoxication which proves unfitness to drive.
Although we are required by our decision in Greiner v. Volkswagenwerk Aktiengeselleschaft, 540 F.2d 85, 89 (3d Cir. 1976), to apply Fisher v. Dye in this appeal,3 Rule 403 of the Federal Rules of Evidence provides that “[ajlthough relevant, evidence may be excluded if its probative value is substantially outweighed by the danger of unfair prejudice. . .. ” We observe that the Pennsylvania decision implicitly requires the same discretionary weighing required by Rule 403. Thus, in interpreting Fisher v. Dye and its progeny, we may draw on our own decisions dealing with review of Rule 403 exercises. This court, speaking through Judge Van Dusen, has said, “[W]e are bound by the trial court’s rulings ... unless the court exercised its discretion arbitrarily or irrationally.” United States v. Alessandrello, 637 F.2d 131, 146 (3d Cir. 1980), cert. denied, 451 U.S. 949, 101 S.Ct. 2031, 68 L.Ed.2d 334 (1981). Speaking specifically to *330the application of Fisher v. Dye by federal courts, we have noted the substantial presumption of correctness that we give to the exercise of the trial court’s discretion. Greiner, 540 F.2d at 90. This deference to the trial judge is appropriate because of his superior position from which to assess the extent of potentially unfair prejudice. He, not the appellate judge, has the totality of the evidence before him, United States v. Long, 574 F.2d 761, 767 (3d Cir.), cert. denied, 439 U.S. 985, 99 S.Ct. 577, 58 L.Ed.2d 657 (1978), and must respond to evidentiary questions as they arise. Therefore, a reviewing court should be hesitant to substitute its own analysis based on a cold record.
III.
Billow v. Farmers Trust Co., 438 Pa. 514, 266 A.2d 92 (1970), upon which the district court relied, makes it clear that the polestar in a trial judge’s analysis under Fisher v. Dye is “unfitness to drive.” Affirming a lower court’s exclusion of expert testimony that a blood alcohol level of 0.14 percent would have “affected” a motorist’s driving, the Billow court held that the offer of proof, by itself, “falls short of the requirement that the evidence show ‘a degree of intoxication which proves unfitness to drive.’ ” Id. at 517, 266 A.2d at 93.4
Appellants argue that, Billow notwithstanding, evidence of elevated blood alcohol level is admissible. They rely on Cusatis v. Reichert, 267 Pa.Super. 247, 406 A.2d 787 (1979), in which the Superior Court reversed a trial court’s exclusion of blood alcohol level although the case did not involve any evidence of wild or erratic driving. See also Schwarzbach v. Dunn, 252 Pa.Super. 454, 461, 381 A.2d 1295, 1298 (1977) (dictum). Cusatis’ seeming contradiction with Billow was discussed in Couts v. Ghion, 281 Pa.Super. 135, 421 A.2d 1184 (1980), in which the Superior Court noted that in Cusatis the evidence of elevated blood alcohol was supplemented by other evidence of drunken behavior. Couts accommodated Billow and Cusatis by pronouncing “evidence of blood alcohol content, when accompanied by other evidence suggesting a high degree of intoxication, is admissible.” Id. at 144, 421 A.2d at 1189. Accepting Cusatis as a relevant precept, we do not believe the district court to have erred. Like the Cusatis court, it recognized that Billow requires supplementary evidence. Although that requirement was satisfied in Cusatis by evidence of drinking and drunken behavior at the scene of the accident, the evidence adduced in this case did not meet the test of showing unfitness to drive.
Appellants contend that the district court erred by conditioning admissibility upon evidence that Rovegno was reckless; they argue that there was evidence that he was negligent. We do not understand the trial judge to have insisted upon a showing of recklessness; in his memorandum opinion he appears to have used “recklessness” in the layman’s sense and as merely one category of “other evidence” along with “excessive speed,” “erratic driving,” and “careless driving,” all of which could be characterized as recklessness, negligence, or neither.5
*331The Pennsylvania decisions have not established a precise level of culpability to be applied as an immutable threshold. To impose a rigid standard for foundation evidence would impair the trial judge’s flexibility to perform his duty of determining whether, in the particular case before him, the evidence and offers of proof present a picture of unfitness to drive sufficiently clear that the probative value of the evidence of drinking or intoxication outweighs its potential for unfair prejudice.
In the instant case, although the jury ultimately found that Rovegno was negligent, its finding is not inconsistent with the trial judge’s conclusion. The judge and jury in their respective duties apply different standards. Although there is evidence that Rovegno’s truck was partly in the passing lane at the time of impact, there was no other evidence which might have constituted a causal connection between Rovegno’s purportedly elevated blood alcohol level and the accident. Indeed, Ward testified that there was nothing unusual about Rovegno’s operation of his vehicle before the accident. Therefore, we cannot say that the trial judge abused his discretion in determining the probative value of this evidence insufficient to overcome the unfairly prejudicial effect of the blood alcohol level evidence.
When presented with an exercise of discretion that is based on matters of narrative fact, a reviewing court must give substantial deference to the trial judge, whose working knowledge of the entire record and opportunity to assess the credibility of testimony put him in an advantageous position. Recently, we noted the limitations on appellate review of discretionary decisions — like the one at issue here — which depend on direct contact with the litigation:
Only the trial judge has seen the witness or observed the jury’s reaction to evidence. ... In those circumstances the trial court has a superior vantage point which an appellate court cannot replicate. The trial court’s decision therefore merits a high degree of insulation from appellate revision.
United States v. Criden, 648 F.2d 814, 817-18 (3d Cir. 1981). We do not believe that this appeal presents a reason to upset the trial court’s decision. The trial judge considered the appropriate factors in light of the relevant Pennsylvania law. Because his decision to exclude the evidence of elevated blood alcohol level was not arbitrary or irrational, it was not an abuse of discretion.
IV.
Accordingly, the judgment of the district court appealed in No. 80-2513 will be affirmed. Leave to withdraw the appeal in No. 80-2512 is granted.
Appellants to bear costs.
. The jury awarded plaintiff $18,250 in the survival action and $170,000 in the wrongful death action. The district court granted defendants’ motion for new trial limited to the issue of damages. A second jury awarded plaintiff $18,630 in the survival action and $191,363 in the wrongful death action. Contending that the second verdict was grossly excessive, appellants argue that the district court erred in refusing to grant a third trial on damages. We disagree. Mathematical exactness is not required of a jury’s damages computation. Vizzini v. Ford Motor Co., 569 F.2d 754 (3d Cir. 1977). The two virtually identical verdicts demonstrate to our satisfaction that the district court did not err in holding that the evidence presented was sufficient to approximate fairly the amount of damages and that the verdict was not shocking to the judicial conscience. See Frankel v. Heym, 466 F.2d 1226, 1228 (3d Cir. 1972); Connolly v. Philadelphia Transportation Co., 420 Pa. 280, 287, 216 A.2d 60, 64 (1966).
. Appellee also filed a notice of appeal from the district court’s denial of her motion for a new trial on the issue of decedent’s pain and suffering, but states in her brief that she withdraws that appeal.
. Speaking through Judge Biggs, we said:
Erie R. Co. v. Tompkins, 304 U.S. 64, 58 S.Ct. 817, 82 L.Ed. 1188 (1938), compels us to follow the law of Pennsylvania. Greiner argues that Fisher v. Dye, 386 Pa. 141, 125 A.2d 472 (1956), established a “black letter rule” in her favor, saying, “.. . while proof of intoxication is relevant where reckless or careless driving of an automobile is the matter at issue, the mere fact of drinking intoxicating liquor is not admissible, being unfairly prejudicial, unless it reasonably establishes a degree of intoxication which proves unfitness to drive.” 386 Pa. at 148, 125 A.2d at 476. Morreale v. Prince, 436 Pa. 51, 258 A.2d 508 (1969) (Roberts, J.).
However, drinking evidence insufficient to establish intoxication can come in if it is coupled with other evidence supporting an inference of intoxication.
Greiner v. Volkswagenwerk Aktiengeselleschaft, 540 F.2d 85, 89 (3d Cir. 1976) (footnote citing Pennsylvania cases omitted).
. Appellants argue that their offer of proof was precisely worded to indicate that the expert testimony would show “unfitness to drive” and that counsel chose this terminology to avoid the result in Billow. We attach no particular significance to the label on an offer of proof because it is not the party proffering the evidence but the trial judge who must determine whether the testimony would unfairly prejudice the jury.
. In denying the motions for a new trial or judgment n. o. v., the district court stated:
The Supreme Court of Pennsylvania has consistently held that proof of intoxication is only relevant where reckless or careless driving of an automobile is a matter at issue. Billow v. Farmers Trust Co., 438 Pa. 514, 266 A.2d 92 (1970). See also Miles v. Ryan, 484 F.2d 1255 (3d Cir. 1973). Defendants’ reliance on Greiner v. Volkswagenwerk, 540 F.2d 85 (3d Cir. 1976), is misplaced. In Greiner there was evidence of reckless driving sufficient to permit the trial judge to submit the alcohol issue to the jury. In the case sub judice there was no such “other evidence” as excessive speed, recklessness or erratic driving on the part of Marshall Rovegno. Therefore submission to the jury of testimony as to intoxication would surely have been unfairly prejudicial.
Mem. op. at 3, reprinted in app. at 193.