Arizona republican., 1922-01-21
MARICOPA COUNTY
TYPE OF HIGHWAY
IS BEST IN TEST

A crucial test OF road types which
has been In progress at Pittsburg
California, since November last
has produced results most gratifying
to the Maricopa county highway com
mission. The test was devised by
Lloyd Aldrich, member of the Ameri
can Society OF Civil Engineers ano
consulting highway engineer of Sar
Francisco, for the purpose Of deter
mining the best type of highway fol
durability. Mr.. Aldrich had no
preference of types and was not serV-
ing any particular type.
Ali were invited into the test and
13 types were submitted. A road
way in the form Of an ellipse 1870
feet in it's longest diameter was
built. The roadway is eighteen feet
in width. Among the types was that
OF the Maricopa county highway with
its new and peculiar cross section de-
vised by Chief Engineer Perkins diff
fering from other types in its deer
9-inch shoulders of the 6-inch slab.
The roadway was completed and
thrown open to the test November g
Only trucks were used in the test
from the lightest to the heaviest D.
ton trucks. They have been con-
stantly driven over the roadway since
then until a week ago tonnage OF
more than 100000 has passed over
the ellipse.,
Mr.. Aldrich arrived in the city a
few days ago bringing with him q
record of the test to date. 1t should
be said that the ultimate thing In
the test is the destruction of the
roadway, and a considerable part of
G an he VxYox
end. At first two liens of trucks
We're driven over it moving in oppo-
site directions but on account Of the
collapse OF some of the section
which had to be repaired in order
that the test may be continued as to
the others, one line of trucks has been
Not only was the ordinary wear
arranged for but trials by impact
were made, first OF an inch and later
OF two inches, giving to the roads
such trial as they would not likely
receive in the ordinary course of use.
Observations Of the effect OF the i'm
pact was made from four tunnels
under the road way where by means
of self recording instruments there
might be shown any swaying of the
road on account of any unevenness
Of the subgrade.
Charts have been made and kept
OF the progress of the test. a sheet
for each type. On the chart such
cracks as appeared before traffic
was put on are indicated by red ink
lines. AS other cracks appeared as
a result of wear they were marked
with pencil along with the date of
their appearance. Account is not
taken of cracks and broken sections
at the joints between sections of diff
ferent types.
All thirteen types are. Of one form
or another OF cement concrete rang
ing from a cost of probably $4,000
a mile at the time of construction
to $4,000. The Maricopa type to
date has stood up better than any
other. In fact its chart shows none
except a half dozen red ink lines
which had already appeared before
traffic was put on the road. There
is not pencil mark on this section
and said Mr.. Aldrich yesterday. the
section appears in every way to be
as good as when the test was begun.
Even at the initial joints there has
been little raveling or cracking. Even
the red lines mark fissures so small,
said Mr.. Aldrich, that many Of them
are hardly noticeable.
The next type in point Of endur-
ance is five-inch steel reinforced
slab. Many of the more
costly types have gone by the board
and can be used further only by