dissenting.
The ultimate question presented by this case is whether the defective dome platform1 which caused petitioner’s injury is a safety appliance within the meaning of § 2 of the Act of April 14, 1910, c. 160, 36 Stat. 298, 45 U. S. C. § 11. The Court holds that the dome platform is a *326“running board” within the meaning of § 2, and that the tank car involved here was a car “requiring” the platform.
First, it can hardly be said that the dome platform is a running board as that term is used in § 2 of the Act. It appears that every device regulated by the Safety Appliance Act is principally designed for use by, and for the protection of, trainmen while railroad cars are in motion. Certainly there is no indication that this legislation was meant to regulate all devices and appliances employed on railroad cars; and there is nothing in the legislative history upon which to base a belief that equipment designed principally for loading and unloading cars, such as a dome platform, was to be covered by the statute. Moreover, while a dome platform might be loosely spoken of as a running board, it does not appear that it falls within the technical definition of that term as used in the trade. ' A running board is a “plane surface, made of boards or special metal structure, for trainmen to walk or run on.” 2 The platform involved here is used principally to stand on to give convenient access to the top of the dome.
However, the principal ground upon which I dissent is aside from the question whether a dome platform is a “running board” under § 2. Assuming that it is, it does not follow that the respondent violated the Act. Pursuant to such an assumption, I will read § 2 of the statute as though the words “dome platforms” appear in the place of “running boards.” But even then not every *327defective dome platform is prohibited by the statute. So far as pertinent here, § 2 provides that “all cars requiring . . . secure running boards [viz., dome platforms] shall be equipped with such . . . .” The congressional mandate then is merely that railroad carriers shall provide secure dome platforms on cars “requiring” them. No other dome platforms would be safety appliances under this Act. Therefore, the inquiry here narrows to whether this tank car “required” a dome platform.
Section 2 does not itself indicate any means for determining which cars require running boards (dome platforms), and thus does not specify which dome platforms, if any, are safety appliances.3 However, § 3 of the Act provides that within six months “the Interstate Commerce Commission, after hearing, shall designate the number, dimensions, location, and manner of application of the appliances provided for by section two of this Act . . .”4 and that those designations are to remain as railroad equipment standards unless changed by the Commission.5 It seems inescapable, just as a matter of *328logic, that since § 3 gave to the Commission the duty to determine, among other things, how many of the “required” § 2 appliances shall be used and where they shall be placed, the Commission was thereby meant to determine which are cars “requiring” running boards (dome platforms), and therefore which dome platforms, if any, are safety appliances. Moreover, if it be assumed that the statute is ambiguous in this matter, the other alternative is to leave to the courts the determination of which types of cars require dome platforms, or any other § 2 equipment except sill steps and handbrakes, to be revealed ad hoc. The creation of such uncertainties is not to be favored. But in view of the existence of the Interstate Commerce Commission, an administrative expert in the safety requirements of the railroad industry, coupled with the explicit delegation to the Commission by § 3 of the authority to designate the number and location of the appliances required by § 2, it would seem difficult to conclude anything but that Congress made railroads responsible as insurers only for such running boards as the Commission, not the courts, might determine are required. This purpose of Congress is even more clear from the words of the Act itself than it is from the Code sections, codified long after the regulations were issued.
This leads me to examine the regulations promulgated by the Interstate Commerce Commission pursuant to § 3 of the Act. As previously noted, that section required the Commission to prescribe the uniform standards applicable to the safety appliances set forth in § 2. Nowhere in the regulations (49 CFR § 131.1 et seq.) does the Commission prescribe dome platform equipment for tank *329cars.6 It follows that tank cars are not cars “requiring” dome platforms. Therefore, the absence of such equipment on tank cars, or the presence of such equipment in a defective condition, should not constitute a violation of the Act. Of course, this would not mean that railroads could with impunity employ insecure dome platforms on their tank cars, or for that matter, any defective equipment not covered by the Safety Appliance Act. That Act does not supplant the basic law of negligence, and this petitioner has preserved his right of recovery for any negligence.
The fact that the Association of American Railroads prescribes dome platforms for tank cars in its safety appliance standards7 does not suggest a different result. The Association is not entrusted with the enforcement of this statute or with its reach; and while it is commendable that it has adopted standards in this instance which require equipment beyond that which may be covered by the Safety Appliance Act, if I am correct as to the duties of the Commission, the action of the Association cannot supplant the determinations of the Commission.
This Court has never before held that railroad car equipment not specifically required by statute or regulation can be treated as governed by the Safety Appliance Act. That issue has been ruled upon in accordance with this dissent in Central Vermont R. Co. v. Perry, 10 F. 2d 132. There the trial court had instructed the jury affirmatively on the application of the Safety Appliance *330Act with respect to the absence of a footboard across the rear of a tender. Without deciding whether the foot-board was a running board within the meaning of § 2 of the 1910 Act, and evidently upon the assumption that it was, the court said:
“As the Safety Appliance Act and its supplements do not require a footboard at the rear end of the tender of a shifting engine and the regulations of the Interstate Commerce Commission do not require one, ... we are of the opinion that the court erred in its instruction to the jury.” Id., at 137.
The position herein expressed is not contrary to Illinois Central R. Co. v. Williams, 242 U. S. 462. That case involved a defective handhold at the top of a ladder on a boxcar. Section 2 of the Act provides for secure ladders on all cars “requiring” them, and, on “all cars having ladders,” it provides for secure handholds at the top of the ladders. The Court commented that “A box car could not properly be used without a secure ladder and . . . all cars having ladders must be equipped with secure hand holds . . . .” Id., at 464. But I do not understand this to have been a holding by the Court that, apart from any Interstate Commerce Commission determination, boxcars require secure ladders. At most the comment was a dictum, since it was clearly not necessary to decide whether the car involved required a secure ladder. The car had a ladder, and all cars “having ladders shall also be equipped with secure hand holds or grab irons on their roofs . . . .” Moreover, as later appears in that case, the Commission had previously issued an order designating the number, dimensions, location, and manner of application of ladders on boxcars. While that order granted an extension of time of five years within which to comply with the standards therein prescribed, it nonetheless constituted a Commission determination that box*331cars require secure ladders within the meaning of § 2. For similar reasons Texas & Pacific R. Co. v. Rigsby, 241 U. S. 33, is not contrary to this dissent. See Atchison, T. & S. F. R. Co. v. Scarlett, 300 U. S. 471.
Finally, continuing to assume that a dome platform is a running board under § 2, and now upon the further assumption that the courts were meant to decide which cars require them, a dissent is still indicated. In these circumstances, consistent with the normal rule, great respect should be given to the interpretation of an act by the administrative agency designated to administer it.8 As has been observed, the regulations of the Interstate Commerce Commission prescribing the uniform standards applicable to § 2 safety appliances omit to mention dome platform equipment for tank cars. Thus the Commission does not understand dome platforms to be “required” for tank cars under § 2. If it had so understood, it is reasonable to believe it would have provided standards for such equipment in its regulations. Moreover, at the request of the Court, the Commission advised by. brief in this case that the dome platform was not even a running board, much less a required running board. Following this Court’s ruling in Davis v. Manry, 266 U. S. 401, this “construction by the Commission — the tribunal to which the application of § 2 is entrusted and which would be solicitous to enforce it — ” should be followed. Id., at 404-405.
For these reasons the judgment should be affirmed.
The device involved in this case is denominated a dome platform in the Car Builders’ Cyclopedia (18th ed. 1949-1951) 253.
Car Builders’ Cyclopedia (19th ed. 1953) 51. Substantially the same definition of the term appears in each of the other eighteen editions of this volume, the first of which was published in 1879 as “The Car-Builder’s Dictionary.” That edition was published so as to alleviate the “inconvenience, confusion, and delay . . . caused . . . by want of common names for the different parts of [railroad] cars.” Preface, The Car-Builders’ Dictionary (1879). See also note 1, supra.
Section 2 does, however, specify which cars require sill steps and handbrakes. “All cars must be equipped with secure sill steps and efficient hand brakes . . . .” (Italics supplied.) Assuming that “sill steps” and “hand brakes” include all devices falling within those terms when used generically, it would seem that all such devices are safety appliances and must meet the statutory standard of “secure” or “efficient.” Cf. Southern Pac. Co. v. Carson, 169 F. 2d 734.
The quoted phrase does not appear in 45 U. S. C. § 12, the Code section corresponding to § 3 of the Act. The phrase evidently was omitted from the Code as being fully executed at the time the Code was compiled.
The Act became law on April 14, 1910. Thus, the Commission had until October 13, 1910, within which to adopt its standardizing regulations. Such regulations were adopted on October 13, 1910, by Commission order. Subsequently, on March 13, 1911, the Commission adopted another order superseding the order of October 13, 1910. 49 CFR § 131.1 et seq. However, the effective date of the mandate *328of § 2 was, by its terms, not until July 1, 1911, over three months after the final promulgation of the Commission regulations. There was thus no time lag, either actual or contemplated, between the effective date of § 2 and the I. C. C. determinations.
49 CFR §§ 131.8 (b) and 131.9 (c) are the only regulations relating to running boards on tank cars, and it is clear, as well as conceded, that those subsections do not require a running board of any sort at or near the dome of these cars.
A. A. R. Safety Appliances for Tank Cars Built after May 1, 1917, Car Builders’ Cyclopedia (19th ed. 1953) 939-942; A. A. R. Code of Rules for the Interchange of Traffic (1952 ed.), Rules 3 (s)(l),3(r)(7).
United States v. American Trucking Assns., 310 U. S. 534, 549.