"The trial court found that the Arizona law had no reasonable relation to safety, and made train operation more dangerous. Examination of the evidence and the detailed findings makes it clear that this conclusion was rested on facts found which indicate that such increased danger of accident and personal injury as may result from the greater length of trains is more than offset by the increase in the number of accidents resulting from the larger number of trains when train lengths are reduced. In considering the effect of the statute as a safety measure, therefore, the factor of controlling significance for present purposes is not whether there is basis for the conclusion of the Arizona Supreme Court that the increase in length of trains beyond the statutory maximum has an adverse effect upon safety of operation. The decisive question is whether in the circumstances the total effect of the law as a safety measure in reducing accidents and casualties is so slight or problematical as not to outweigh the national interest in keeping interstate commerce free from interferences which seriously impede it and subject it to local regulation which does not have a uniform effect on the interstate train journey which it interrupts."[823] THE LESSON OF SOUTHERN PACIFIC CO. _v._ ARIZONA The lesson to be extracted from Southern Pacific Co. _v._ Arizona is a threefold one: 1) Where uniformity is judged by the Court to be "essential for the functioning of commerce, a State may not interpose its regulation"; 2) in resolving this question the Court will canvass what it considers to be relevant facts extensively; 3) its task is, however, in the last analysis, one of weighing competing values, in brief, arbitral rather than strictly judicial.