ocal shipments to be furnished on demand,
were held to be invalid.[806] In the first brace of decisions, the
application of the local regulation to interstate commerce was found
not to be "unduly" burdensome; in the second brace the contrary
conclusion was reached.

SAFETY AND OTHER REGULATIONS

A class of regulations as to which the Court has exhibited marked
tolerance although they "incidentally" embrace interstate transportation
within their operation are those which purport to be in furtherance of
"public safety."[807] The leading case is Smith _v._ Alabama,[808] in
which the Court held it to be within the police power of the State to
require locomotive engineers to be examined and licensed, and to enforce
this requirement until Congress should decree otherwise in the case of
an engineer employed exclusively in interstate transportation. Also
upheld as applicable to interstate trains were a statute which forbade
the heating of passenger cars by stoves;[809] a municipal ordinance
restricting the speed of trains within city limits;[810] the order of a
public utility commission requiring the elimination of grade
crossings;[811] a statute requiring electric headlights of a specified
minimum capacity;[812] a statute requiring three brakemen on freight
trains of over twenty-five cars.[813] In the last case the Court
admitted that "under the evidence," there was "some room for
controversy" as to whether the statute was necessary, but thought it
"not so unreasonable as to justify the Court in adjudging it" to be
"merely an arbitrary exercise of power" and "not germane" to objects
which the State was entitled to accomplish.[814] And in 1943 the Court
sustained, though again in somewhat doubtful terms, the order of a State
railroad commission requiring a terminal railroad which served both
interstate and local commerce to provide caboose cars for its
employees.[815] At times, indeed, the Court has made surprising
concession to local views that had nothing to do with safety. Hennington
_v._ Georgia,[816] decided in 1896, where was sustained a Georgia
statute forbidding freight trains to run on Sunday, is perhaps the
supreme example. Whether such an act would pass muster today is
doubtful. And earlier statutes reinforcing the legal liability of
railroads as common carriers and the carriers of passengers were
sustained in the absence of legislation by Congress.[817]

INVALID STATE REGULATIONS

"The principle that, witho