This action arose as a consequence of a grinding head-on collision on Highway 91, approximately 15 miles south of Cedar City, Utah. There were no survivors and no eye witnesses. Plaintiff, the administrator of the estate of Terry and Constance DeMille, husband and wife, commenced this wrongful death action against the estate of Frederick Kenneth Spendlove. During the course of the trial, at the close of the evidence, both parties moved for a directed verdict. The court found that all the testimony indicated the collision between the two cars occurred near the center of the highway, but there was no question that the DeMille vehicle, operated by Terry DeMille, was two to four feet over the center line at the point of collision on a bright, clear day. The court ruled that Terry DeMille was negligent, as a matter of law, in the operation of his vehicle, i. e., he failed to keep a proper lookout and drove on the wrong side of the road, where there was an approaching automobile. However, the court submitted to the jury the issue of the negligence of Spend-love in the death of Constance DeMille. The jury returned a verdict in the amount of $23,000 for her wrongful death. Defendant appeals and seeks a reversal of the *280judgment of the trial court or in the alternative a new trial.
The record reveals that there are very-few facts concerning this action. There was evidence that Terry DeMille intended to seek employment in Las Vegas, Nevada. The DeMilles were observed entering a service station in Cedar City on the morning of August 11, 1965, at approximately 6:30 to 6:40 a. m. The Highway Patrol received notice of the accident,at 6:55 a. m. There was no evidence presented in regard to Spendlove, but evidently from the sparse facts, it was concluded that the DeMille vehicle, a Chevrolet, was traveling south, and the Spendlove vehicle, a Volkswagen, was traveling north on the two-lane highway. There was a five-inch segmented white line dividing the highway and a solid four-inch yellow line in the west lane (the southbound lane). Both vehicles were found on the east side; Spend-love’s Volkswagen was off the pavement, and the DeMille’s Chevrolet was located approximately in the center of the east lane.
Two investigating officers of the Highway Patrol were called as witnesses, William R. Burch and Robert J. Reid; they testified as to the physical evidence they observed and to the opinions they formed therefrom. They were unable to estimate the speed of the vehicles, but the speed limit was 60 miles per hour. Officer Burch estimated that from the scene of the accident there was a visibility of 300 to 400 yards toward the south, and that as he approached the scene from the north he could observe the vehicles for several hundred feet or maybe several hundred yards. No explanation was proffered as to-the purpose of the solid yellow line in the west lane, nor its relative length in relationship to the vicinity of the accident. There was no physical evidence to indicate that the driver of either vehicle took any evasive action prior to the collision.
The two officers testified extensively about the marks and gouges upon the highway surface. However, all of this physical evidence occurred subsequent to the moment of impact of the vehicles. The scuffs and gouges nearest to the approximate area of the initial impact were within the east lane of the highway; the skid marks appearing in the west lane occurred after the vehicles disengaged and were-spinning out of control prior to their proceeding to their final positions. Plaintiff has placed great emphasis on the first mark made upon the highway surface; it is a scuff mark about 20 inches wide and approximately 60 inches from the center line, which was apparently made by the-right front tire of the Volkswagen as it left striations in the pavement and then ultimately collapsed. (The Volkswagen was-60 inches wide and 56 inches from tire to tire.) A measurement from this scuff mark indicated that the Volkswagen at that *281moment was 1/2 to 2y2 inches onto the eastern side of the five-inch white line. Plaintiff has urged that this constituted evidence that the decedent, Spendlove, was not in his own lane. Officer Burch was of the opinion that the Volkswagen changed ■direction upon impact, which placed it closer to the center line than it previously was. Officer Reid was of the opinion that the Volkswagen did not change direction until after the initial marks were made. Neither officer could identify the exact positions of the vehicles at the moment of impact. A careful reading of the record reveals that there is an insufficient amount of evidence to determine as a matter of fact whether the Volkswagen was actually ■on the white line, although admittedly close to it. A choice of probabilities creates ■only a basis for conjecture on which a verdict of a jury cannot stand.1
Officer Burch further testified that it was his opinion that the Chevrolet was three to four feet across the white line at the time of impact; that the area of impact did not extend over the white line; and that he did not find any evidence to indicate the Volkswagen was on the wrong side of the road. Officer Reid expressed no opinion as to these matters.
On appeal, defendant contends that the trial court erred by failing to direct the verdict in favor of the Spendlove estate. Defendant asserts that plaintiff had the burden of proving his right to recover by a preponderance of the evidence,' and that it was not within the province of the jury to indulge in mere speculation or conjecture with respect to the issue of negligence. Since there was no evidence produced at the trial in regard to the acts and conduct of the deceased, Spendlove, prior to the collision, and the events leading up to the accident were unknown, defendant claims there was no competent evidence upon which the trial court could submit the issue of Spendlove’s negligence to the jury.
There was a presumption, based on the instinct of self-preservation, that the deceased, Spendlove, was exercising due care for his own safety; this presumption may take the place of evidence sufficient to make a positive finding in the absence of other evidence.2 However, once the opposing party produces a prima facie case as to the nonexistence of this presumed fact, the presumption disappears. It is a question for the court whether a prima facie case has been established. If the court concludes that the opposing party has failed to produce sufficient evidence to overcome the presumed facts and such facts are dispositive of the case, the court should direct a verdict in accordance *282therewith.3 In the instant action the trial court erred by instructing the jury on the presumption that Spendlove exercised due care; either the presumption disappeared or the court should have directed the verdict in favor of the defendant. The latter alternative was the correct course.
Defendant further contends that the trial court erred by submitting to the jury in Instruction 24, five separate issues upon which they could predicate negligence on the part of Spendlove, namely, that it was his duty to maintain a proper lookout; to keep the car under reasonably safe and proper control; to drive as nearly as practicable entirely within a single lane and not to move from one lane to another until he has ascertained that he could do so with reasonable safety; to keep his automobile on his own right side of the highway; to turn his vehicle to the outside of the highway to avoid a collision. Defendant asserts that this instruction consisted of mere abstract propositions of law, which were unconnected to the issues involved, and that there was no competent evidence to which the jury could apply them.
* * * the duty of an automobile driver, who is on the right side of the street, to stop or take other precautions to avoid a collision with an approaching vehicle, only arises when by due care he discovers that another on the wrong side of the street cannot or will not himself turn to the right to clear his way. It follows that his right to assume that the other driver will comply with the laws of the road is not absolute, but may be qualified by the particular circumstances, such as the other vehicle’s proximity, position and movement and the condition-of the road, including the usable width.4
Plaintiff’s entire case is predicated on' the assumption that Spendlove had ample-time and space to avert the accident;5 there is no evidence in this regard. One may only speculate as to the circumstances immediately prior to the collision, i. e., did the DeMille vehicle suddenly swerve to the left; was the DeMille vehicle obscured by another vehicle, which DeMille was commencing to pass while the yellow line was in his lane; did either vehicle have a sudden mechanical failure; did DeMille observe the Volkswagen in the west lane and incorrectly conclude that it could not return to the east lane in time so DeMille swerved to the east; or was DeMille, as contended by plaintiff, cruising down the east lane for a sufficient time and distance that Spendlove in the exercise of due care should have taken appropriate evasive action?
*283Instruction 24 permitted the jury to speculate as to the circumstances prior to the accident; any evasive action which it may have been Spendlove’s duty to take would be dependent upon factors which were not in evidence. The trial court erred in giving Instruction 24, which merely advised the jury about abstract principles of law, which had no relation to any issue or evidence in the case.6
In the instant action, from the evidence adduced there is no basis upon which reasonable minds could find that the ■decedent, Spendlove, abrogated his duty of due care in the operation of his motor vehicle, which proximately caused the death of Constance DeMille. "The showing of a mere possibility that the accident might have been avoided is insufficient.”7 The trial court erred by its denial of defendant’s motion for a directed verdict.
TUCKETT and HENRIOD, JJ„ concur.. Alvarado v. Tucker, 2 Utah 2d 16, 19, 268 P.2d 986 (1954).
. Compton v. Ogden Union Ry. & Depot Co., 120 Utah 453, 457, 235 P.2d 515 (1951).
. Tuttle v. Pacific Intermountain Express Co., 121 Utah 420, 429, 431, 242 P.2d 764 (1952) ; Mecham v. Allen, 1 Utah 2d 79, 85, 86, 262 P.2d 285 (1953).
. 2 Blashfield Cyclopedia of Automobile Law and Practice, § 919, pp. 97-98.
. Howard v. Ringsby Truck Lines, 2 Utah 2d 65, 71, 72, 269 P.2d 295 (1954).
. Stapley v. Salt Lake City Lines, 18 Utah 2d 214, 418 P.2d 779 (1966); Morrison v. Perry, 104 Utah 151, 160, 140 P.2d 772 (1942).
. Howard v. Ringsby Truck Lines, footnote 5, supra, at p. 72, 2 Utah Reports, 2d, 269 P.2d at p. 300.