In 1970 Allen Ostergar died from injuries suffered in an automobile accident on State Highway 26 near Blackfoot, Idaho. Ostergar owned the Dodge van in which he was riding, but it was being driven by Joseph Gooch, who also died as a result of the accident. The collision occurred when the van was driven into the rear of a pickup truck that had been stopped on the highway by the flagman of a State Department of Highways repair crew. The crew was under the immediate supervision of their foreman, James F. Mansfield.
The surviving heirs of Ostergar originally brought an action against several parties 1 alleging liability for the death of Ostergar. Mansfield was among those defendants. The complaint alleged that he wantonly and willingly failed to move the appropriate warning signs up the highway as the work progressed. Thus, the complaint continued, the accident occurred due to Mansfield’s gross negligence in failing to warn adequately the oncoming drivers.
The district court granted Mansfield’s motion for summary judgment pursuant to I.R.C.P. 56. From that order, this appeal is taken.
Ostergar’s surviving heirs, hereinafter referred to as appellants, assign as error the district court’s determination of contributory negligence by Gooch and imputing that negligence to Ostergar pursuant to I.C. § 49-1404(1), thus precluding any action by appellants. The appellants also assign as error the trial court’s failure to find the doctrine of contributory negligence unconstitutional, and the trial court’s failure to hold that contributory negligence is not a defense to allegations of gross *531negligence. For the reasons stated below we do not find it necessary to discuss those issues.
We affirm the order of the district court, but on a theory different from that relied upon by the lower court. Rinehart v. Farm Bureau Mutual Insurance Company of Idaho, Inc., 96 Idaho 115, 524 P.2d 1343 (1974); Lemmon v. Hardy, 95 Idaho 778, 519 P.2d 1168 (1974).
A summary judgment is proper only in the absence of a genuine issue of material fact. I.R.C.P. 56(c); Fairchild v. Olsen, 96 Idaho 338, 528 P.2d 900 (1974). This determination is based upon all pleadings, affidavits, depositions, and admissions in the record, and all facts contained therein are to be liberally construed in favor of the appellant. City of Weippe v. Yarno and Associates, 96 Idaho 319, 528 P.2d 201 (1974); Fairchild v. Olsen, supra.
In light of these requirements, the record discloses that the conditions of the accident were as follows: the Ostergar van, driven by Gooch, approached the work site on a dry highway, with one-quarter to one-half mile of clear visibility as a result of the full daylight; the pickup truck with which the van collided had been stopped by a highway crew flagman wearing a fluorescent red vest and holding a red paddle-type stop sign; the flagman was standing near the pickup; Mansfield, hereinafter referred to as respondent, had failed to move the warning signs up the highway as he told a co-worker he would do;2 the Ostergar van collided with the rear of the stopped pickup truck, throwing that vehicle approximately 285 feet into the sagebrush beside the road; there is no evidence that the van either slowed down or swerved prior to the collision.
Within that factual framework the appellants allege that Mansfield’s conduct constituted a negligent act resulting in Ostergar’s death. The analysis of a negligence question requires consideration of both factual cause and legal cause of the injury. Henderson v. Cominco American, Incorporated, 95 Idaho 690, 518 P.2d 873, (1973); Prosser, Handbook of the Law of Torts, §§ 41, 42 (4th ed. 1971) (hereinafter cited as Prosser). As the Court stated in Henderson at page 695, 518 P.2d at page 878, “ * * * proximate [legal] cause focuses upon legal policy in terms of whether responsibility will be extended to the consequences of conduct which has occurred, [citations omitted] * * * [while] actual cause * * * is a factual question focusing on the antecedent factors producing a particular consequence [citations omitted].”3 The relationship is well explained by Professor Green as, “It is the defendant’s conduct [actual cause] that inflicts the hurt, but it is the law [legal cause] that makes his conduct negligent.” Green, The Causal Relation Issue, 1962, 60 Mich.L.Rev. 543, 551 (hereinafter cited as Green). Thus, the threshold question of negligence analysis is whether the conduct of the defendant was a substantial factor in bringing about the injury suffered by the plaintiff.
Although the determination of the factual cause of an injury is normally left to a jury, the court may perform that function as a matter of law when the undisputed facts can lead to only one reasonable conclusion. Schaefer v. Elswood Trailer Sales, 95 Idaho 654, 516 P.2d 1168 (1973); Baker v. Barlow, 94 Idaho 712, 496 P.2d 949 (1972). We believe this to be such a situation. The record does not support a contention that the conduct of Mansfield was a factor in the death of Ostergar.
The driver of an automobile is held to have notice of that which is plainly *532visible on the highway before him. Yearout v. Chicago, Milwaukee, St. P. & P. R. Co., 82 Idaho 466, 354 P.2d 769 (1960); Whiffin v. Union Pac. R. R. Co., 60 Idaho 141, 89 P.2d 540 (1939). The repair site was identifiable by the flagman, the pickup truck, the various vehicles of the repair crew, and the members of the crew. All this was clearly visible from a considerable distance. The Ostergar van drove directly into the parked pickup truck. To find that Mansfield’s failure to erect yellow, four-foot by four-foot warning signs was an actual cause of Ostergar’s death would require a finding that those signs would have provided more notice of the blocked highway than did the obvious blockage itself. This we cannot do. Therefore we find that Mansfield’s conduct was not an actual cause of Ostergar’s injury. Henderson v. Cominco American, Incorporated, supra; Anderson v. Parson Red-E-Mix Paving Company, 24 Utah 2d 128, 467 P.2d 45 (1970); Sturdevant v. Kent, 322 P.2d 408 (Okl.1958); Martin v. Smith, 103 Cal.App.2d 894, 230 P.2d 679 (1951); Prosser, supra; Green, supra.
Mansfield’s activity was not a factual cause of Ostergar’s injury and renders moot the assignments of error concerning contributory negligence.
For the reasons stated above the judgment of the district court is affirmed. Costs to respondents.
McQUADE, C. J., and McFADDEN and SHEPARD, JJ., concur.. This group included the State of Idaho, the members of the Idaho Board of Highways, and the Department of Highways. All of these were subsequently dismissed as party-defendants, and that dismissal was affirmed by this Court in Munson v. State Department of Highways, 96 Idaho 38, 524 P.2d 166 (1974).
. This is disputed by Mansfield but assumed arguendo for the purpose of this analysis.
. While this Court designates factual cause as “actual cause” and legal cause as “proximate cause,” other courts include both factual and legal cause under the general term “proximate cause.” Although this conflict in terminology oft times complicates the analysis, a careful reading of the cases cited normally clarifies the terminology therein utilized.