Gloucester County Democrat. (Woodbury, N.J.) 1878-1932, 1908-05-14

rock dust hung to the horizon and marked
the speeding course Of the big machine was
the sight witnessed by travellers on the ia
NOUS conduit road dozen miles from
Washington on Thursday, April %.
The seemingly pronounced violation of
the speed ordinances was eountenaneed by
two of the Nations federal departments;
Agriculture and War; however; the rush
ing motor car having been pressed into
requisition by L. w Page, Director of the
Office of Public Roads, and DR.. Allerton S.
Cushman, Assistant Director, in the effort
to determine the effects OF automobile traf-
ic upon macdam highways, and the stretch
of thoroiare was placed at their disposal by
War Department. officials.
While the racing car and Others Of various
weights and types made many trips over
the selected stretch of mile and half at
varying rates of speed, from 5 to IS miles
an hour, corps OF skilled photographers,
equipped with the most modern devices for
photographing vehicles at very high speeds,
made accurate records of the various tests.
1t has long been known to highway engl
neers that automobiles were rapidly short
ening 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 surface that not only witnstands,
but improves under the constant passing
and repassing Of vehicles with iron tires,
one must be apprised briefly of the theory
on which, first Tresanget Of Limoges, and
later MacAdam Of Ayr, worked when Civ
ing such highways TO the world. They
reasoned that road surfaced with bits of
stone would improve under wagon traffic be-
cause the iron tires of the passing vehicles
would constantly crush the stones and form
rock dust particles; that those rock dust
particles would not merely fill in all the
interstices between the stones, but would
also form a surface dust binder; the wet
tings and rollings tending TO cement the
dust into shell-like surface and thus make
the entire road one Notwithstanding,
water shedding mass.
They reasoned we'll and wisely. The ma
cadam roads lived up to the theories of
their inventors and improved with the pas
sing years until the advent Of the automo-
bile. :. 1t was but short time after it came
into vogue that highway engineers in all
civilized lands learned that new condition
was confronting them and that established
customs were being menaced. The trouble
was quickly traced so the automobile and it
was studied. 1t was soon noted that the
soft rubber tire was the highway menace.
1t crushed no rock itself and therefore con-
tribubed no quota Of the needful surface
dust binder, while the tremendous tractive
force Of the rear wheels drew up the dust
made by the iron tired wagons and
seat it whirling away over adjacent lands.
Those who witnessed the experiments of
Thursday near the National Capital could
not doubt for moment that the various
road experts all over. the world are correct in
she opinion that very rapidly driven auto
mobiles are rapidly tearing up the surface
OF the macadam road, for not only were
huge clouds of dust lifted into the air and
blown of the road, but careful examination
showed that the material under the wheel
tracks of the machine was distinctly loosen
ed and raYelled even during the short period
Of these tests
No such effects were noticeable after the
passing Of iron tired vehicles the series of
tests beginning with the passing of horse
drawn vehicle. This was photographed as
it moved along and also as the wagon tires
passed a given mark. Then the automo-
biles were sent over the course. The fret
was heavy weight touring car moving at
FIVE miles an hour. A series Of pictures was
made of that car on its many journeys at
varying rates OF speed until its maximum
of IS miles an hour was attained Then
the work was taken up by the huge racer,
which tore down the road first at speed of
so miles an hour, then at 55, 60, and finally
at 65. Ii fairly lifted the road surfacing
material as it speed along, regular ridges of
rock dust rising in front Of She rear wheels
and floating away in binding clouds. Other
tests were made and other pictures taken of
various types OF heavy Limousine cars and
runabouts. Il was plainly noticeable and
was commented on that the automobiles
when moving at the slow rates Of speed
equal to the speed made by horse drawn
vehicles made very little dust, the theory
that fast speeding automobiles are response
BILE for road surface destruction being pretty
thoroughly substantiated by these means.
The results Of this interesting bit of road