utes without having first
obtained from a director of public works a certificate of public
convenience, is primarily not a regulation to secure safety on the
highways or to conserve them, but a ban on competition and, as applied
to a common carrier by motor vehicle of passengers and express purely in
interstate commerce, is both violation of the Commerce Clause and
defeats the express purpose of Congressional legislation rendering
federal aid for the construction of interstate highways.[836]

TRANSPORTATION AGENCIES

The special characteristics of motor travel have brought about a
reversal of the Court's attitude toward State control of transportation
agencies. Sustaining in 1941 a California statute requiring that agents
engaged in negotiating for the transportation of passengers in motor
vehicles over the highways of the State take out a license, Justice
(later Chief Justice) Stone, speaking for the Court, said: "In Di Santo
_v._ Pennsylvania,[837] this Court took a different view * * *, it held
that a Pennsylvania statute requiring others than railroad or steamship
companies, who engage in the intrastate sale of steamship tickets or of
orders for transportation to and from foreign countries, to procure a
license by giving proof of good moral character and filing a bond as
security against fraud and misrepresentation to purchasers, was an
infringement of the Commerce Clause. Since the decision in that case
this Court has been repeatedly called upon to examine the
constitutionality of numerous local regulations affecting interstate
motor vehicle traffic. It has uniformly held that in the absence of
pertinent Congressional legislation there is constitutional power in the
States to regulate interstate commerce by motor vehicle wherever it
affects the safety of the public or the safety and convenient use of its
highways, provided only that the regulation does not in any other
respect unnecessarily obstruct interstate commerce."[838]

NAVIGATION; GENERAL DOCTRINE

In Gibbons _v._ Ogden[839] the Court, speaking by Chief Justice
Marshall, held that New York legislation which excluded from the
navigable waters of that State steam vessels enrolled and licensed
under an act of Congress to engage in the coasting trade was in conflict
with the act of Congress and hence void. In Willson _v._ Blackbird Creek
and Marsh Co.[840] the same Court held that in the absence of an act of
Congress, "the object of which was to control