Mr. Justice Rehnquist
delivered the opinion of the Court.
While proceeding up the Columbia River, the oil tanker S. S. Santa Maria, bareboat chartered by petitioner, was struck by a barge owned by respondent Oliver J. Olson & Co. The barge was being towed by the tugboat San Ja-cinto, owned by respondent Star & Crescent Towboat Co. Both vessels were damaged. Petitioner commenced this admiralty action for damages to the Santa Maria, and respondent cross-libeled for damages to the barge. The District Court found the collision resulted solely from negligence on the part of the crew of the San Jacinto, and dismissed the cross-libel. 304 F. Supp. 519 (Ore. 1969). The Ninth Circuit affirmed the finding that the San Jacinto had been negligent, but determined that the Santa Maria was also negligent in violating the “half-distance” rule, 30 Stat. 99, 33 U. S. C. § 192. That court therefore reversed with directions that the District Court determine the amount of damage sustained by the barge and assess damages under the divided-damages rule. See The Schooner Catherine v. Dickinson, 17 How. 170 (1855). We granted certiorari, 405 U. S. 954 (1972), principally to consider petitioner’s request that we abandon the divided-damages rule. The orderly disposition of the issues presented by the petition for certiorari, however, requires that we address ourselves to the issue of liability before reaching the question of damages. Since in so doing we conclude that the Court of Appeals was wrong in holding the Santa Maria liable at all, we do not reach the issue of damages.
I
On the evening of December 24, 1967, the Santa Maria, loaded with 17,000 tons of petroleum products, was proceeding up the Columbia River toward Portland. The ship was steaming on the Oregon side of the channel, with clear visibility. At the same time, the San Jacinto was proceeding downriver, towing a 275-foot barge, fully loaded with lumber, by a 250-foot towline. Proceeding on the Washington side of the channel, it had encountered foggy weather conditions upriver. As the San Jacinto approached Cooper Point, the Santa Maria, steaming upstream, sighted the tug both visually and by radar. The two vessels were more than a mile apart and on opposite sides of the 500-foot-wide shipping channel. There was heavy fog, described as “tule fog,” around Cooper Point, but the fog was localized on the Washington side of the channel. Although there was haze and drizzle, there was no fog on the Oregon side of the channel; the visibility from the bridge of the Santa Maria upstream was between one and one-half and two miles.
As the San Jacinto entered the fog on the Washington side off Cooper Point, the Santa Maria lost visual contact with the tug and barge. The Santa Maria’s pilot did not track the San Jacinto on radar, believing that the tug would remain on the Washington side of the channel and knowing that there was ample room for a port-to-port passage. At this time, the Santa Maria was proceeding at half-speed making approximately seven knots.
The watch on the San Jacinto had not sighted the Santa Maria when the tug entered the heavy fog off Cooper Point. The tug’s captain testified that, after entering the fog, he cut speed to three or three and one-half knots, and the visibility dead ahead was approximately 50 yards. The San Jacinto’s navigators were “navigating by visual sight of the Washington coast,” and the captain estimated that the tug passed between 50 and 75 yards off Cooper Point. At that point, the crew of the San Jacinto heard one blast of a ship’s horn (later discovered to have been that of the Santa Maria), and responded with the fog signal for a tug with a barge in tow. No visual sighting of a ship was made, however. Shortly thereafter, the captain sighted range lights, which, he testified, he thought were 20 degrees off his starboard bow. To avoid what he anticipated to be a momentary collision, the captain swung the San Jacinto to port — towards the Oregon side of the channel — and executed a U-turn, hoping to run upriver and thus avoid a collision.
The San Jacinto started the U-turn while still in the heavy fog, and the execution of the turn brought the tug on a course directly across that of the Santa Maria. The Santa Maria sighted the San Jacinto emerging from the fog, at right angles to the Santa Maria, at a distance of approximately 900 feet. Full astern was immediately ordered. The San Jacinto, quickly completing the turn, headed safely upriver. Before the Santa Maria could completely stop, however, the barge in tow sideslipped across the channel, crashing into the port bow of the Santa Maria; the force of that blow drove the tanker aground.
The District Court found that the San Jacinto and the barge, and those in charge of navigation, were negligent in eight respects, including navigating at excessive speed, failing to maintain a proper lookout, and “acting hastily and without sufficient cause in pulling the tow across the channel when there was adequate clearance for the tug and barge to pass port to port.” The court found that “the collision was proximately caused by the sole fault and negligence” of the San Jacinto and the barge, and that the acts of negligence allegedly committed by the Santa Maria did not “proximately [contribute] to the collision and resulting damage.” 304 F. Supp., at 521, 522.
The Ninth Circuit partially reversed, holding that the Santa Maria was proceeding at an immoderate speed in traveling at three to seven knots “while approaching the edge of the fog bank.” That court reasoned that the San Jacinto was only 900 feet from the Santa Maria when the tug emerged from the fog bank, and the Santa Maria’s, speed was such that she could not stop within half that distance. The court, relying on The Silver Palm, 94 F. 2d 754 (CA9), cert. denied sub nom. United States v. Silver Line, Ltd., 304 U. S. 576 (1937), deemed it immaterial that the visibility up the Oregon side of the channel — the direction in which the Santa Maria was headed — was almost two miles, because in its view the “relevant distance” for calculating the proper speed under the half-distance rule was the distance between the tanker and the fog bank — to port of the Santa Maria. Finding statutory fault, and ruling that petitioner had failed to prove that that fault could not have possibly contributed to the collision, see The Pennsylvania, 19 Wall. 125 (1874), the Court of Appeals held the Santa Maria liable for half the total damages.
II
The question of the liability of the Santa Maria turns on the application of Art. 16 of the Inland Rules of Navigation, 33 U. S. C. § 192. That Rule provides in pertinent part:
“Every vessel shall, in a fog, mist, falling snow, or heavy rainstorms, go at a moderate speed, having careful regard to the existing circumstances and conditions.” (Emphasis added.)
Although the statutory test for determining the proper speed at which a vessel should proceed in a fog is phrased in general terms, our decisions have attached a well-recognized gloss to that phrase. This gloss on the statutory rule, variously referred to as the half-distance rule or the “rule of sight,” is that, in a fog, “a moderate speed” is that
“rate of speed as would enable [the vessel] to come to a standstill, by reversing her engines at full speed, before she should collide with a vessel which she should see through the fog.” The Nacoochee, 137 U. S. 330, 339 (1890).
See also The Colorado, 91 U. S. 692, 702 (1876); The Umbria, 166 U. S. 404, 417 (1897). As stated in The Chattahoochee, 173 U. S. 540, 548 (1899), “[t]he principal reason for such reduction of speed is that it will give [both] vessels time to avoid a collision after coming in sight of each other.” If two vessels, upon sighting each other, are proceeding at rates of speed such that each can stop before it reaches the point at which the courses of the two intersect, collision is impossible.
There can be no quarrel with the salutary purpose of this “rule of thumb.” It is premised on the notion that when a ship is traveling under foggy weather conditions in waters in which other ships might be proceeding on intersecting courses, the speed of each ship must be such as to enable her to stop within half the distance separating the ships when they first sight each other. Implicit in the rule, however, is the assumption that vessels can reasonably be expected to be traveling on intersecting courses. If, on the facts of the case, it is totally unrealistic to anticipate the possibility that a vessel will travel on a particular heading that would intersect the course of another ship, the reason for the rule is rather clearly not present.
Those cases in which this Court has upheld a finding of statutory fault because of a violation of the half-distance rule involved ships proceeding in fog on established coastal shipping lanes, The City of New York, 147 U. S. 72 (1893); The Nacoochee, supra; cf. The Colorado, supra (Lake Huron), or ships traveling near or in a harbor, The Umbria, supra; cf. The Ludvig Holberg, 157 U. S. 60 (1895) (no fault). We do not imply that because a vessel is running near fog, as opposed to running in it, the vessel is not required to proceed at “a moderate speed” in relation to the distance to the fog cover. That was, indeed, the circumstance in The Silver Palm, supra, upon which the Ninth Circuit relied. But there a naval cruiser was traveling, with clear visibility ahead but with fog banks on each side, on the busy coastal shipping lane between San Francisco and Los Angeles. On such a course it is reasonable to expect that another ship might steam out of the fog at right angles to, and on a collision course with, the first vessel. The rule of sight was applicable there precisely because of the reasonable possibility that such an event might occur.
The facts of our case were significantly different. The Santa Maria and the San Jacinto were proceeding on opposite sides of a well-defined and relatively narrow channel. The Santa Mrnia had last sighted the tug only a mile ahead, proceeding along the Washington coast. Those in charge of the navigation of the tanker cannot be faulted for not anticipating the tug’s totally unorthodox maneuver in darting across such a channel. The Victory & The Plymothian, 168 U. S. 410 (1897). The visibility in the direction in which the Santa Maria was headed was almost two miles. There is no evidence in the record suggesting that the speed of the tanker would have prevented her from coming to a complete halt within half the distance of sighting a vessel that was either proceeding on a remotely foreseeable intersecting course or else being overtaken by her. The tug emerged from a fog bank only 900 feet from the tanker on a course and for reasons that no seaman could, under the circumstances, have anticipated.
The District Court’s finding that any negligence on the part of the Santa Maria did not “proximately [contribute] to the collision” was but another way of saying that fault based on the half-distance rule must have some relationship to the dangers against which that rule was designed to protect. Here it did not. We believe that the District Court, and not the Court of Appeals, reached the correct result on the issue of liability.
Since in our view respondents alone were at fault, there is no occasion to consider how damages should be apportioned were both vessels at fault.
Reversed.