This is a negligence case wherein plaintiff sought images from the State of Oregon for injuries she curred in an automobile accident, which occurred on public highway maintained by defendant. The ap;al concerns the propriety of the trial court directing verdict for defendant and its refusing to admit cer-in testimony of plaintiff’s witness.

On December 13, 1976, plaintiff was injured in a ngle-car accident. She was a passenger in the vehicle rich struck the side wall of a freeway entrance ramp iding from the Morrison Bridge in Portland, Oregon, íe weather was clear and the pavement was dry. The iver of the vehicle testified that she hit something ck just prior to losing control of her vehicle and íen she regained consciousness following the acci-nt she noticed that there was gravel and debris on e freeway ramp. Due to freezing fog in the Portland ea on December 1st and 2nd of 1976, defendant’s aintenance department had sanded that area of the ghway including the bridge ramps. After the icy nditions dissipated, on December 3rd, the maine-nce crews began sand sweeping operations. The pervisors responsible for sweeping the Morrison idge ramp could not say whether it had been swept.

It was plaintiff’s theory that the vehicle had en-mtered sand on the entrance ramp and due to the luced friction on the banked curve of the ramp the ver lost control. She alleged that the state had a ty to remove the sand and that is was negligent in ling to do so. The state entered a general denial and its first affirmative defense alleged that it was mune from suit. ORS 30.265(3)(c). Defendant >ved to strike the affirmative defense. The court 'erred ruling until trial but then never did rule on j motion to strike.

At the close of plaintiff’s case in chief defendant ted without putting on evidence and moved for a ected verdict on the ground that plaintiff had failed *328 to prove causation. The trial court acknowledged that plaintiff had presented sufficient evidence from which the jury could have found that there was sand on the highway and that it caused the driver to lose control, but the court granted the motion for the reason that there was no evidence presented of the standard of care against which the defendant’s conduct should be judged.

A directed verdict should be entered only in the exceptional case where, from the facts taken in the light most favorable to plaintiff, reasonable persons could draw one inference and that inference being that defendant was not negligent. James v. Carnation Co., 278 Or 65, 67-69, 562 P2d 1192 (1977).

Plaintiff presented evidence, by way of deposition testimony of the two maintenance supervisors who had the responsibility over this particular bridge ramp, that sand is removed from the highway for safety purposes. One supervisor stated that five days would have been sufficient time to sweep the entire area of all the sand that had been spread. They both testified as to what maintenance activities, including sand removal, that their crews were engaged in between the 3rd and the 13th of December. They both recognized the hazards of reduced traction in areas of banked curves.

There is evidence from which the jury could have found that defendant had a duty to sweep the sand it had spread based on its knowledge of the danger the sand presented to motorists. The general standard of care is the necessary complement of duty. The standard of care required of defendant is that it act as a reasonable person would under the circumstances. This is a question of fact. From the evidence presented the jury could have determined that the priority given to sand removal on this particular ramp was unreasonable. In this instance the jury was capable of deciding what was reasonable conduct. The plaintiff had made *329 prima facie case of negligence and it was error for e trial court to direct a verdict for defendant.

Plaintiff’s second and third assignments of error ncem the exclusion of certain testimony by one of >r expert witnesses. Since our reversal on the direct-verdict issue will necessitate a new trial we will Idress these two other assignments.

We begin our discussion by noting that the proprie-of admitting expert opinion evidence and in deter-ining qualifications of expert witnesses rests largely the discretion of the trial court and its determina-m will not be disturbed on appeal absent abuse. Myers v. Cessna Aircraft, 275 Or 501, 553 P2d 355 (1976). The appellate court can, however, review the idence to decide whether the expert testimony ould have been admitted. Meyer v. Harvey Aluminum, 263 Or 487, 489, 501 P2d 795 (1972). The trial art found that the plaintiff’s witness, who was asked give an expert opinion regarding the priority that ould be given to sand removal from particular areas, 1 not have the requisite expertise to qualify him to stify on that issue. We agree. The fact that plaintiff’s tness, an engineer, had reconstructed many traffic údents in the past and that he was well informed out the effects of sand on a dry highway did not ike him an expert on highway maintenance. The rty offering the expert testimony must carefully set th the qualifications of the witness to give an opin-i on a particular subject. Myers v. Cessna Aircraft, supra, 275 Or at 520. Further, the testimony of the jhway maintenance supervisors was before the jury, was aware of the areas which had been swept and ; other projects which had been undertaken by the dntenance crews. The reasonableness of the defend-t’s assessment of priorities was not a subject on ich the jury needed expert testimony to aid it in its decision.

In her final assignment plaintiff contends that the *330 expert should have been permitted to answer the following question:

"Q. That’s okay. I understand. That’s sufficient. Mr. Sutherland, based upon your expert knowledge and experience and your knowledge of the facts of this case and those that are in evidence and your examination of the Morrison Bridge 1-5 ramp, can you express an opinion as to what the probable result will be if a pickup truck and the tires were in good condition and traveling at 30 miles an hour encountered an accumulation of sand as depicted on Exhibit 14 where Linda Botel has marked an 'A’ on the ramp at the time when that pavement was dry, do you have an opinion?

"A. Yes

"Q. Would you state your opinion?”

The court sustained defendant’s objection on the ground that the hypothetical question was based on unknown facts.

This question put to the witness asked for his expert opinion on the cause of the accident. This was an ultimate fact of the case. An expert may testify to an opinion on an ultimate fact if that ultimate fact cannot be equally well decided by the trier of fact from the same evidence upon which the expert based his opinion. Yundt v. D & D Bowl’ Inc., 259 Or 247, 258-59, 486 P2d 553 (1971); Ritter v. Beals et al, 225 Or 504, 525, 358 P2d 1080 (1961). In this instance, the witness had previously testified that an accumulation of sand on dry pavement would tend to decrease the coefficient of friction and would diminish the driver’s control over her vehicle. The jury had been apprised that the accident occurred at an inclined curve on the bridge ramp. The jury did not need expert testimony to draw the conclusion on the ultimate fact for it. In both instances the trial court was correct in excluding plaintiff’s witness’s testimony.

Reversed and remanded for new trial.