The Mankato free press. [volume] (Mankato, Blue Earth County, Minn.) 1879-1924, 1908-05-22
THE AUTOS AND ROADWAYS.

A two ton racing automobile NOV
ing at something in excess of mile
a minute, while an inpenetrable, cloud
of fog-grey rock dust hung to the hor-
lion and marked the speeding course of
the big machine. was the sigh witnes-
sed by travellers on the famous conduit
road a dozen miles from Washington
Oh Thursday. April %. The seeming
pronounced violation of the speed or
dinances was countenanced by two of
the nations federal departments. agri-
culture and war. However, the rush
ing motor-car having been pressed
into requisition by L. w. Page, di-
rector of the office of public roads.
and DR.. AllertonN s. Cushman, as
sstant director, in the effort to de-
termine the effects of automobile traf-
fic upon macadam highways, and the
stretch of thoroughfare was placed at
their disposal by war department. Off
cials. While the racing car and others
of various weights and types made
many trips over the selected stretch
of a mile and half at varying rates
of speed, from five to siXtyfve miles
an hour. corps of skilled photogra-
pliers, equipped with the most modern
devices for photographing vehicles at
very high speeds, made accurate rec
ords of the various tests.
1t has long been known to high
way engineers that automobiles were
rapidly shortening the lives of the rock
surface roads of the world, and many
experiments have been made in the
past six or seven years to determine
the actual cause of the damage done.
To understand how the soft broad tires
of the modern motor car can work an
injury to a surface that not only
withstands, but improves under the con-
slant passing and repassing of vehicles
with iron tires, one must be appraised
briefly of the theory on which, first
Tresauget of Limoges, and later Mac
such highways to the world. They
reasoned that a road surfaced with
bits of stone would improve under
wagon traffic because the iron tires
of the passing vehicles would constant
ly crush the stones and form rock
dust particles; that those rock dust
particles would not merely fill in all
the intersticcs between the stones but
would also form surface dust binder
the MEETINGS and rollings tending to
fl,n 1,,cf ,pfA oh
face and thus make the entire road
one of traffic withstanding, water
shedding mass.
They reasoned well and wisely. The
macadam roads lived up to the theories
of their inventors, anu improved with
the passing years until the advent OF
the automobile. 1t was but short
time after it came into vogue that
highway engineers in all civilized lands
learned that new condition was con.
fronting them and that established
customs were being menaced. The
trouble was quickly traced to the au
tomobile and it was studied 1t was
soon noted that the soft rubber tire
was Ihe highway mehace. III crushed
no rock itself and therefore contri
buted no quota of the needful surface
dust binder, while the tremendou:
tractive force of the rear wheels drew
up the dust made by the iron tired
wagons and sent it whirling away
over adjacent lands.
Those who witnessed the experiment
of Thursday near the pational capito
could not doubt for a moment thai
the various road experts all over th'
world are correct in the opinion thai
very rapidly driven automobiles ar,
rapidly tearing up the surface of thu
maeadam road, for not only were