"The principle that, without controlling Congressional action, a State may not regulate interstate commerce so as substantially to affect its flow or deprive it of needed uniformity in its regulation is not to be avoided by 'simply invoking the convenient apologetics of the police power.'" So remarks Chief Justice Stone in his summarizing opinion cited above, in Southern Pacific Co. _v._ Arizona.[818] Among others he lists the following instances in which State legislation was invalidated on the basis of this rule: "In the Kaw Valley case[819] the Court held that the State was without constitutional power to order a railroad to remove a railroad bridge over which its interstate trains passed, as a means of preventing floods in the district and of improving its drainage, because it was 'not pretended that local welfare needs the removal of the defendants' bridges at the expense of the dominant requirements of commerce with other States, but merely that it would be helped by raising them.' And in Seaboard Air Line R. Co. _v._ Blackwell,[820] it was held that the interference with interstate rail transportation resulting from a State statute requiring as a safety measure that trains come almost to a stop at grade crossings, outweigh the local interest in safety, when it appealed that compliance increased the scheduled running time more than six hours in a distance of one hundred and twenty-three miles."[821] And "more recently in Kelly _v._ Washington,"[822] the Chief Justice continued, "we have pointed out that when a State goes beyond safety measures which are permissible because only local in their effect upon interstate commerce, and 'attempts to impose particular standards as to structure, design, equipment and operation [of vessels plying interstate] which in the judgment of its authorities may be desirable but pass beyond what is plainly essential to safety and seaworthiness, the State will encounter the principle that such requirements, if imposed at all, must be through the action of Congress which can establish a uniform rule. Whether the State in a particular matter goes too far must be left to be determined when the precise question arises.'" STATE REGULATION OF LENGTH OF TRAINS