The plaintiff, Kimberly Ann Jackson, sued on account of injuries sustained in a collision with a bicycle on October 2, 1978, on the parking lot adjoining the apartment building in which she and her parents lived. She was four years old at the time. The defendants were the owner and the operator of the apartment building. The petition charged that the defendants had failed to make the parking lot reasonably safe. She .recovered a verdict of $850,000, which is not challenged before us. The trial court set the verdict aside and entered judgment for defendants. The court also sustained an alternative motion for new trial, finding error in the verdict directing instruction. The Court of Appeals affirmed. We granted transfer and, taking the case as on original appeal, now reverse and direct the entry of judgment on the verdict. We of course are obliged to accept the facts which most strongly support the verdict.
The apartment complex consists of two buildings of 30 units each. A driveway with a 12 to 17 percent grade adjoins the complex on the west. A person going down the hill in a southerly direction passes successively the first building, a parking lot, and the second building (in which the plaintiff and her family lived), before reaching the lower parking lot where the accident took place. As many as 40 cars might be parked in the lower lot. The corner of the second building obscures the view of the lower parking lot from the driveway. To the east of the apartment complex is a trailer park, also owned by the defendants.
The accident occurred between 5 and 6 P.M. The plaintiff’s father, Michael Jackson, was the only eyewitness. He was working on his car in the lower parking lot when the plaintiff’s mother sent her to tell him that dinner was ready. His attention was attracted by a shout of “watch out” *666and he saw a formation of three bicycles, with one ahead of the others. The plaintiff “froze” and the leading bicycle struck her. Although Jackson’s testimony is not entirely clear and consistent, he stated that the point of impact was 55 feet east of the southwest corner of the building, and that the plaintiff ended up 75 feet from the southwest corner.1 He could not estimate the speed of the bicycle because he saw it only momentarily.
The plaintiff adduced as an expert witness Boulter Kelsey, a consulting mechanical engineer. He testified over objection that, in his opinion, the bicycle which struck the plaintiff was traveling at least 24 feet per second, or 16.4 miles per hour, at the time of the collision. He reached this conclusion on the basis of a “straight drag calculation” on the assumption that plaintiffs body had traveled 20 feet, and said that neither the weight of her body nor that of the cyclist or the cycle was material.2
Kelsey testified that, in his opinion, a safety bump should have been installed diagonally across the driveway as it reached the entrance to the lower parking lot. The bump should be designed to prevent a bicycle from crossing at a speed greater than 10 miles per hour. At a higher speed the cycle would “become airborne” and could not turn in the air. If a bicycle were slowed to 3 or 4 miles per hour it could accelerate to approximately 11 miles per hour in the 55 foot distance to the point of the accident. Kelsey said that safety bumps were standard safety devices for use in parking lots for the purpose of slowing the speed of automobiles and other vehicles.3
There was ample evidence that boys were wont to drive their bicycles at substantial speed down the hill and into the lower parking lot, and that several complaints had been made to the resident manager before the accident. The boy whose cycle injured plaintiff lived with his family in the trailer park to the east. A path had been worn between the trailer park and the lower parking lot.
Ray Kruse, a representative of the defendants, testified that he was not aware of any complaints about bicycles in the parking lot until after the plaintiff was injured. He was aware of the use of speed bumps but asserted that they existed for the purpose of controlling automobile traffic. (The jury of course did not have to accept this conclusion, and could have accepted Kelsey’s testimony that a bump was appropriate to control bicycle speed.) Kruse expressed doubt that a building permit would be issued for a speed bump but had made no effort to find out. He had no other suggestion for dealing with speeding bicycles unless a guard were posted to warn cyclists off the parking lot. The defendants had another piece of property, of a very different nature, which had a speed bump at the time they acquired it.
The problem before us of course is whether the plaintiff should be allowed to go to the jury on the evidence presented. We are indebted to Judge Welliver for his research into scholarly writings about tort law. Our courts have followed the traditional analysis of negligence cases into the elements of duty, breach of duty and causation. Virginia D. v. Madesco Investment Corp., 648 S.W.2d 881 (Mo. banc 1983); Hoover’s Dairy, Inc. v. Mid-America Dairymen, 700 S.W.2d 426 (Mo. banc *6671985). A landlord owes a duty to its tenants, strongly emphasized in recent cases, to make common portions of the leased premises reasonably safe.4 This includes the duty to take notice of known dangers and to institute needed corrective measures. The duty extends to driveways and parking lots where there are problems about the speed of vehicles. See Clifton v. Brown, 253 Ark. 148, 484 S.W.2d 884 (1972), suggesting a speed bump as at least one possible precaution.
We of course must take the case as the parties present it. The plaintiff elected to go to the jury solely on the claim that the defendants were negligent in not installing a speed bump. She supported her claim with the testimony of an adequately-qualified expert, who expressed the opinion that a speed bump was indicated as a means of protection against speeding bicycles. He was not cross-examined as to other possibilities, and the defendants made no additional suggestions of safety measures, either through their principals or by expert testimony. The defendants also disclaimed knowledge of any problem with speeding bicycles. With the state of the record as it is, the jury could find that the defendants had notice of a condition which required the installation of a speed bump and were negligent for failing to provide it. It would be contrary to the course of the law for us to substitute our judgment for that of the jury as to whether the only safety precaution suggested was necessary, in the exercise of due care.
The defendants argue vigorously, however, that the plaintiff has not established the element of causation. The accident was precipitated, of course, by the bicycle rider, who no doubt could be faulted for excessive speed and inattention. There may, however, by more than one proximate cause of an accident. Green v. Kahn, supra. As Judge Welliver’s opinion demonstrates, the subject of causation has been the subject of much discussion among legal scholars, often because of bizarre hypothet-icals such as the one in which two persons fire at a third at the same time, with each inflicting a wound which would have been fatal without regard to the other shot. Another favorite has a person furnishing to another a car with brakes he knows to be defective, with the driver making no effort to apply the brakes. A recent article summarizing the views of the several distinguished commentators is that of Professor Richard W. Wright. 73 Cal.L.Rev. 1737 (Dec.1985) “Causation in Tort Law.”
This case would be characterized by Professor Wright as one of “doubtful” causation, akin to a case involving a public swimming pool in which a child drowns while the lifeguard is absent. It is extremely difficult to prove that the drowning would not have occurred if the lifeguard had been present, but it would certainly be reasonable for a jury to conclude that the presence of a lifeguard would make the chances of rescue “more likely than not.” Professor Wright argues that no more should be required and his view has substantial support.5 There are obvious difficulties in this case in setting up a counterfactual situation which definitively projects the sequence of events under the assumption that a safety bump had been in place. Striving for certainty is a tour de force. The jury must deal in terms of probabilities.
The defendants point to gaps in the proof, such as the absence of evidence of the speed of the bicycle proceeding down the hill, of the condition of the brakes and steering mechanism, and of the attentiveness of the rider. They also argue that there is no substantial evidence that the *668bicycle was traveling at a speed of 16.4 miles per hour at the time of the collision. Then, as a backup, they argue that, based on Kelsey’s own testimony, the bicycle could have crossed the bump at the rated speed of 10 miles per hour, and, for all that the evidence shows, could have accelerated to 16.4 miles per hour at the point of collision.
The defendants, however, would unreasonably circumscribe the jury’s authority to draw inferences from the evidence. The figure of 16.4 miles per hour is based on expert opinion. The defendants did not challenge the expert’s qualifications, nor did they present any contrary testimony. The jury could have accepted the 16.4 mile per hour figure. We lack the means for disagreeing with the expert. The jury also could have found that the bicycle, aided by the downhill grade, had reached a speed of 16.4 miles per hour or more by the time it entered the parking lot, that the rider made no attempt to check his speed, at least until he heard the shouted warning, and that, by that time, he was unable stop the bicycle soon enough to avoid the collision. These conclusions are not speculative; they are logical and permitted inferences from the evidence.
The jury, indeed, could have found that the bicycle was traveling substantially faster than 16.4 miles per hour at the time it reached the level of the parking lot and that the rider was in the process of applying the brakes as he struck the plaintiff, so that the bicycle traveled only a few feet after the collision. The jury might believe that the rider had heard the shouted warning and that, had the speed of the bicycle been checked by a bump, he could have brought it to a stop in time to avoid an accident.
The defendants also make much of Kelsey’s testimony that, if the cycle were slowed to a speed of 3 to 4 miles per hour by the bump, it could reach a speed of 11 miles per hour at the point of impact. They suggest that, had there been a speed bump which could be crossed at 10 miles per hour, the rider might have been able to accelerate to 16.4 miles per hour at the time of the collision. If so, they argue, the speed bump would not have prevented the collision, and there is a fatal flaw in the evidence of causation. This argument is based on the unrealistic assumption that the rider, after crossing the bump, would then accelerate to the maximum degree. There may be some confusion in Kelsey’s reference to a speed of 3 to 4 miles per hour, but the defendants should have addressed their uncertainties to the jury rather than to the appellate courts, and perceived gaps should have been flushed out in cross-examination. The jury could properly find that a speed bump would have slowed the cyclist, making it more likely that he would have heard a warning or would have seen the plaintiff in time to avoid the collision. An alternate finding could be that, if the rider approached the parking lot at full speed and in ignorance of the presence of the bump, or if he knew of the bump and still approached it without reducing his speed, the bicycle would have been propelled in the air in a direction in which it would not have presented a danger to the plaintiff.
We have expounded at some length on the implications of Kelsey’s testimony to demonstrate that the jury could have believed a speed bump at the place he suggested could have greatly reduced the chance of an accident, either by slowing down the bicycle or shifting its direction. No more should be required. The law deals with probabilities. Virginia D. v. Madesco, supra; Wright, supra, pages 1809-1813. An analogy is found in Racer v. Utterman, 629 S.W.2d 387, 394 (Mo.App.1981), in which Judge Gerald M. Smith opines that, in a “failure to warn” case, it is not necessary to show with certainty that the warning would have prevented the casualty. Also in line is our recent opinion in Nesselrode v. Executive Beechcraft, Inc., 707 S.W.2d 371 (Mo. banc 1986), which approved a failure to warn submission, with regard to parts which could be improperly switched, even though it could not be said with certainty that warnings placed directly on the parts would have been seen *669and heeded. Causation is an element of products liability cases just as it is of negligence cases, and so the cases just cited are pertinent.
Our conclusion is consistent with Missouri cases applying the “substantial factor” test of causation.6 We find nothing in the literature cited by Judge Welliver or in the cases cited by diligent counsel which conflict with our conclusion. Returning to Judge Welliver’s argument that the finding of duty is predominant, our holding is simply an application of the strong policy requirement that a landlord use due care in making common areas safe for tenants. This duty may require the use of appropriate safety devices. The jury is the arbiter of due care and reasonableness. One purpose of the law of torts is to encourage people to take precautions.
The dissent raises the spectre of liability of the landlord to a bicyclist who is injured by a speed bump. The suggestion interjects a foreign issue. The scope of the duty is very different from that of a landlord to a tenant. Patterson v. Gibson, 287 5.W.2d 853 (Mo.1956). Dividers, ties, and bumpers are usual in parking lots, and their presence does not furnish a basis for finding negligence. Hopkins v. Sefton Fibre Can Co., 390 S.W.2d 907 (Mo.App.1965).
The trial judge, quite properly, made a conditional ruling on the motion for new trial. He did not act on any discretionary ground but found that the plaintiff’s verdict directing instruction7 was not supported by the evidence. The defendants seek to justify this ruling by arguing absence of evidence of proximate cause. No arguments are made in addition to those tendered on submissibility. Inasmuch as we find that the plaintiff made a submissi-ble case, we perceive no error in the verdict director. The grant of the new trial, then, was not proper.
The judgment is reversed and the case is remanded with directions to enter judgment on the verdict.
BILLINGS and RENDLEN, JJ., concur. HIGGINS, C.J., concurs in separate opinion filed. DONNELLY, WELLIVER and ROBERTSON, JJ., dissent in separate opinions filed.. During closing argument, defense counsel argued:
At the time that Mr. Jackson brought his little daughter in there they quote him as saying that she was moved or knocked ten feet as a result of the impact. In the courtroom he said twenty feet....
The engineer was not cross-examined as to whether the difference between 10 feet and 20 feet was significant. According to the evidence the plaintiff was airborne for part of the distance and slid or rolled for the remainder.
. Kelsey testified that height and weight of the victim and of the cyclist would be critical to a determination of exact velocity, but that, to determine minimum velocity less information is necessary.
. Kelsey also suggested that there should be another bump further up the driveway.
. Green v. Kahn, 391 S.W.2d 269 (Mo.1965); Barker v. East Side Building Corporation, 344 S.W.2d 299 (Mo.App.1960); Hieken v. Eichhorn, 159 S.W.2d 715 (Mo.App.1942).
. Rovegno v. San Jose Knights of Columbus Hall Ass’n, 108 Cal.App. 591, 291 P. 848, 850 (Cal.Dist.Ct.App.1930) and Collins v. Riverside Amusement Park Co., 61 Ariz. 135, 145 P.2d 853, 857 (1944) (whether failure to provide lifeguard was the proximate cause of drowning held to be issue for jury). See also, Prosser, Proximate Cause in California, 38 Cal.L.Rev. 369, 382-383 (1950).
. On the "substantial factor" test of causation, see Restatement (Second) of Torts, § 431 (1965); Ricketts v. Kansas City Stock Yards Co. of Maine, 484 S.W.2d 216 (Mo. banc 1972); and Todd v. Watson, 501 S.W.2d 48, 52 (Mo.1973). See also Giles v. Moundridge Milling Co., 351 Mo. 568, 173 S.W.2d 745, 750 (1943); Stumpf v. Panhandle Eastern Pipeline Co., 354 Mo. 208, 189 S.W.2d 223, 227 (1945); and Champieux v. Miller, 255 S.W.2d 794, 797 (Mo.1953). We do not agree with Judge Donnelly’s suggestion that the substantial factor test was devised to respond to the riddle of concurring events, each independently sufficient to cause the injury. The riddle would remain. The substantial factor test, rather, was intended to demonstrate that the precipitating cause (here the actions of the cyclist) is not necessarily the only legally sufficient cause. A cause which meets the substantial factor test is a cause in fact.
. INSTRUCTION NO. 6
Your verdict must be for plaintiff if you believe:
First, there was no speed control bump at the curve at the bottom of the hill in the driveway and as a result the driveway was not reasonably safe, and
Second, defendants knew, or by using ordinary care could have known, of this condition, and
Third, defendants failed to use ordinary care to make the driveway reasonably safe, and Fourth, such failure either directly caused injury to plaintiff or combined with the acts of Shawn Amsden to directly cause injury to plaintiff.