This is an action to recover damages for personal injuries suffered by plaintiff when his automobile and the automobile of defendant Taylor collided in a dense cloud or plume of smoke which settled on the highway as a result of field burning by defendant Venell. Plaintiff charged defendant Taylor with negligence in the operation of his automobile and charged defendant Venell with negligence in failing to post signs or other warning devices indicating dense smoke for approaching traffic.
The facts are not in dispute. On September 5, 1972, plaintiff collected air samples in an area of field burning south of Corvallis, Oregon. "While returning to Corvallis, through a smoky area, he suddenly came upon a ball or plume of particularly dense smoke, which prompted him to slow and then stop his vehicle on the roadway. Defendant Taylor was driving at approximately 75 miles an hour in the same direction as plaintiff. He began to slow his car when he first saw plaintiff enter the cloud of smoke one-quarter to one-half mile ahead of him. When he saw plaintiff disappear into the dense plume about 200 yards ahead, Taylor tried to slow down but was unable to do so sufficiently to avoid striking the rear of plaintiff’s car.
The smoke had come from the burning of defendant Venell’s field adjacent to the road. Venell had a burning permit from the Philomath Eire Department and had checked the wind direction prior to igniting his field to prevent crop disease. After the fire began, the wind shifted sending smoke across the road. Be*145cause the fire could not be stopped at that point without making the smoke thicker, it was allowed to continue burning. The accident occurred about five minutes after the change in wind direction.
On defendant’s motion, the trial court struck plaintiff’s allegation that defendant Venell was negligent “in failing to post signs or other warning devices indicating dense smoke” for approaching traffic. Plaintiff contends that this constitutes reversible error.
The question is whether a farmer, burning field grass adjacent to a highway, has a duty to post signs or other warning devices to inform motorists who are aware of the existence of smoke on the highway that dense smoke is ahead.① From a practical standpoint if such a duty were imposed, it would require every farmer burning his field to post such a warning because he could never know in advance whether the smoke would pass over the highway in a dispersed or concentrated form. The imposition of such a stringent duty might well be justified if the failure to warn could be regarded as a substantial factor in alerting motorists of the danger which lay ahead of them. But we agree with the trial judge that warning devices would not have this significance where the approaching motorist has knowledge that smoke has drifted upon the highway ahead of him. In those circumstances, the motorist is warned that danger lies ahead and that it may be great or small, depending upon the density of the smoke on the highway. To impose upon the defendant a duty to warn the plaintiff of that which he will himself discern would place an unneces*146sary burden upon the defendant. Stated in another way, under the circumstances we have before us, the failure to post warnings cannot be considered a causal factor contributing to plaintiff’s harm.②
Judgment affirmed.
This is not to be confused with the question of whether a defendant could be negligent for causing smoke to go upon the highway. The trial court recognized that there could be negligence for such conduct even as to a motorist who had knowledge of the existence of the smoke on the highway. That issue was submitted to the jury and it returned a special verdict that Venell was not negligent in this respect.
We do not intend to hold that there could not be negligence arising from a failure to warn in a situation where the approaching motorist would not otherwise be made aware of the presence of smoke on the highway. We agree with the cases cited in the dissenting opinion which hold that failure to warn under such circumstances may constitute negligence. See e.g., Shelton v. Lowell, 196 Or 430, 249 P2d 958 (1952); Dokken v. Rieger, 255 Or 433, 467 P2d 968 (1970); and Moore v. Plymouth, 249 N C 423, 106 SE2d 695 (1959). Other cases cited such as Austin Road Company v. Evans, 499 SW2d 194 (Tex Civ App 1973); Boob v. Fisher, 225 Md 278, 170 A2d 298 (1961); and Hinkel v. Weyerhaeuser Co., 6 Wash App 548, 494 P2d 1008 (1972), seem to indicate that a warning might be necessary on the facts of the present case. We find these cases unpersuasive.