September 6, 1953, Peter Kiewit Sons’ Company, pursuant to a contract with the highway department of the state of Washington, was engaged in repair and maintenance work approximately one-half mile west of the summit of Snoqualmie Pass on U. S. highway No. 10. In performing this work, the main traveled portion of the highway was barricaded, and a gravel-surfaced detour constructed adjacent to the highway for a distance of approximately five hundred feet.
One approaching the detour from the west was confronted at varying intervals with the following warning road signs: At four hundred feet from the detour, “Speed 25 M. P. H.”; at three hundred feet, “Detour Ahead”; at two hundred fifty feet, “Slow” and “No Passing”; at two hundred feet, “Loose Gravel”; at one hundred feet, “Keep to the Right.” After the last sign, there were lighted flares (after dark) at fifty-foot intervals along the right edge of the detour for its entire length. The graveled detour left the concrete pavement at an angle of approximately thirty-five degrees and re-entered upon the pavement at the same angle.
On Sunday, September 6, 1953, at approximately eight-thirty p. m., George Argus was traveling on a motorcycle in an easterly direction along the five-hundred-foot graveled *855detour. As he left the detour to return to the paved portion of the highway, the front wheel of his motorcycle struck a depression, or trough, three to four inches deep, between the edge of the pavement and the gravel. The impact threw him over the handlebars of the motorcycle. This action, which alleged negligence in the company’s maintenance of the detour, was brought to recover damages for physical injuries and property damage.
The evidence established that the defendant corporation had kept an employee on duty for the entire day, who sprinkled the temporary graveled detour and kept it graded. The employee testified that he graded the area three times on the Sunday in question, the last time being at approximately six o’clock in the evening, and that, when he left the road, it was in as good condition “as it was humanly possible to get it.” The resident engineer inspected the road every few hours. The last inspection was at seven o’clock p. m., at which time the engineer found the detour to be in a satisfactory condition.
Defendant’s motions for nonsuit and for a directed verdict were denied. The jury returned a verdict in favor of the plaintiff. The trial court denied defendant’s motions for judgment notwithstanding the verdict and for a new trial. Judgment was entered upon the verdict, and the defendant corporation has appealed.
The appellant, relying upon Muskatell v. Queen City Constr. Co., 3 Wn. (2d) 200, 100 P. (2d) 380 (1940), contends that it is not liable for injuries received by motorists using the detour because, in maintaining the detour, it was acting pursuant to a written contract with the state highway department, and the work was performed in accordance with the department’s plans and specifications. In the cited case, the court emphasized that nonliability presupposes the absence of negligence and said [p. 202]:
“The rule is that, where a city, acting within its general powers, contracts for improvement upon a street, and the work is done by a contractor in accordance with the plans and specifications furnished by the city, he is the agent of the city and is not liable for damages in the absence of neg*856ligence in the performance of the work. [Citing cases.]” (Italics ours.)
See Palin v. General Constr. Co., 47 Wn. (2d) 246, 287 P. (2d) 325 (1955); 27 Am. Jur. 533, § 53; 69 A. L. R. 489, 493.
Whether there was negligence on the part of the corporation in the performance of the work under its contract presented a factual question to be determined by the jury.
Appellant next contends that, unless or until the contractor, in the exercise of due care, is shown to have had actual or constructive notice of the defect a sufficient length of time before the accident to have remedied the condition, there can be no liability.
The duty of the appellant contractor to use ordinary care in keeping the detour in a safe condition for proper travel involved the anticipation of defects that were the natural and ordinary result of use by vehicular traffic. Appellant could not remain passive until the defect or dangerous condition developed and an accident happened, and then avoid liability on the ground that it had no actual or constructive knowledge or notice of the specific defect or the dangerous condition. In the exercise of due care, it had a duty to anticipate the development of a dangerous condition and guard against it. In the proper exercise of due care, the appellant is chargeable with knowing what might reasonably be expected to happen. Dillabough v. Okanogan County, 105 Wash. 609, 178 Pac. 802 (1919); 25 Am. Jur. 738, §446.
The court did not err in denying appellant’s motion to dismiss upon the grounds urged.
Appellant assigns as error the court’s instructions Nos. 2 and 13.
Instruction No. 2 is as follows:
“The court rules as a matter of law that the affirmative defense, wherein the defendant alleges contributory negligence on the part of the plaintiff with regard to speed and point of entry onto the paved portion of the highway, has not been established by the evidence, and I therefore withdraw same from your consideration.”
*857The appellant pleaded contributory negligence in the following language:
“That if plaintff sustained any injuries or damage as alleged in his complaint, the same were solely and proximately caused or substantially contributed to by his own negligence in failing to exercise ordinary care under the circumstances then prevailing at the time and place in question, and in failing to follow the directional signs and warnings in place at said location with regard to speed and point of entry onto the paved portion of the highway from said detour.”
The affirmative defense put in issue three alleged acts of negligence on the part of the respondent: (1) excessive speed, (2) failure to exercise ordinary care at the point of entry onto the paved portion of the highway, and (3) failure to heed the directional signs.
By instruction No. 2, the court determined, as a matter of law, that the appellant had not established two of the claimed acts of negligence on the part of respondent, which were (1) failure to exercise ordinary care, under the circumstances, with regard to speed, and (2) failure to exercise ordinary care at the point of entry onto the highway. In so doing, the court invaded the province of the jury. Whether the admitted speed of the driver of five to ten miles an hour was excessive, or whether the claim of such speed was impeached by the physical fact of the driver of the motorcycle being thrown over the handlebars and onto the paved portion of the highway, or whether the admitted speed was excessive for one operating a motorcycle (proceeding with due regard for his own safety), when approaching the pavement at a thirty-five degree angle from a loose gravel road, were questions of fact to be determined by the jury. There was evidence concerning the issue of respondent’s speed upon which the minds of reasonable men could differ.
Secondly, by instruction No. 2, the court found, as a matter of law, that respondent had exercised due care in operating his motorcycle at the point of entry upon the pavement from the graveled detour. It was for the jury to determine whether, under the facts of this case, a motorcycle *858operator, when cautioned that there was a detour and loose gravel ahead, in the exercise of due care for his own safety-might reasonably expect to find a trough three to four inches deep at the point where the graveled detour abutted the concrete pavement.
The law relating to contributory negligence was submitted to the jury in instruction Ño. 8, but, the court having specifically taken consideration of two of the three alleged acts of contributory negligence from the jury, instruction No. 8 could relate only to the alleged failure of respondent to heed the directional signs and warnings.
It was prejudicial error to have given instruction No. 2.
Instruction No. 13 is as follows:
“You are instructed that the defendant as a contractor in charge of the work on the highway in question had the duty to maintain all detour areas in a reasonably safe condition for vehicular traffic. In so maintaining the detour areas the defendant must use such care as a reasonably prudent person would use under the same or similar circumstances.
“Under the law of this state Vehicular traffic’ includes all types of legally licensed vehicles, including motorcycles.”
We have held that one charged with proper maintenance of a highway must maintain it in a reasonably safe condition for one who is operating a motor vehicle in a lawful manner and exercising due care for his own safety under the circumstances then and there existing. Berglund v. Spokane County, 4 Wn. (2d) 309, 313, 103 P. (2d) 355 (1940); Owens v. Seattle, ante p. 187, 191, 299 P. (2d) 560 (1956). Although a contractor is charged with maintaining a detour in a reasonably safe condition, his duty has been performed if the highway is in a reasonably safe condition for those using it in a lawful manner, and who are exercising due care for their own safety. In Owens v. Seattle, supra, at p. 184, we said:
“A municipality is not an insurer against accident nor a guarantor of the safety of travelers. It is, however, obligated to exercise ordinary care to keep its public ways in a reasonably safe condition for persons using them in a proper manner and exercising due care for their own safety. [Citing case.]” (Italics ours.)
*859Instruction No. 13 placed upon the contractor the duty “to maintain all detour areas in a reasonably safe condition for vehicular traffic.” The instruction placed upon the contractor a greater duty to repair under these circumstances than our decisions require. A three to four inch rut might well be considered by a jury as not a reasonably safe condition for vehicular traffic generally, whereas a three to four inch rut might well be considered by a jury as a reasonably safe condition for vehicular traffic proceeding in a lawful manner, each vehicle being driven by one exercising due care for his own safety. It is the latter rule which has been adopted, establishing and limiting the extent of the contractor’s duty to repair.
Instruction No. 13 improperly defined the contractor’s duty with reference to maintenance. It was prejudicial error to have given the instruction in its quoted form.
Instructions Nos. 9 and 10 properly defined respondent’s duty as a user of the highway. These instructions did not cure the improper statement of the law which attempted-to define the extent of the contractor’s duty with reference to maintenance and repair.
We have not discussed each of the assignments of error involving similar instructions. However, upon a new trial, the instructions given should conform with the views expressed herein.
We find no merit in appellant’s remaining assignments of error.
For the reasons stated, the judgment is reversed and the cause remanded, with instructions to grant appellant’s motion for a new trial.
Hill, C. J., Don worth, Weaver, and Foster, JJ., concur.