Minnesota Highways, April 1955

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VOL.  4,  NO.  6
1246  University Ave., St.  Paul 4, Minn.
APRIL,   1955
In Springtime
Load Limits Aid Highways
Spring's arrival, once more dreaded by the Maintenance
division than a dozen howling blizzards — and more expensive
— now is as welcome to the division as to young lovers and
j^^ition hungry school children.
^^P No longer do the combination of spring thawing and
heavy traffic make many miles of Minnesota highways look
like the aftermath of an aerial bombardment — pockmarked
with holes and gaping cracks.
Springtime traffic now moves with a minimum of interference and delay. Emergency repair crews are conspicuous
by the comparative infrequency of their appearance.
All this despite a tremendous increase in the number of
motor vehicles in the state, with the number of registered
trucks, now about 215,000, nearly double the total of two
decades ago.
Protection and maintenance of
Minnesota highways during the
spring breakup period has advanced a great distance since the
state's trunk highway system was
instituted in 1921 — and the savings in road-user tax dollars have
run into many millions.
Much of this is due to improved
construction of the newer roads,
for the thousands of miles of
■ roads continuing in use, the
explanation — and salvation — lies
mainly in the Highway department's spring-time road restriction
program and the high degree to
which the trucking industry cooperates to make the program successful.
Each year, more than 7,000
miles of the 11,900-mile trunk
highway system are restricted for
varying periods as to the gross axle
weight of vehicles which may use
them. The restriction periods usually range from six to eight weeks
for a given area, the maximum per-
missable gross loads from three to
seven tons per axle.
Also, all county and township
roads in Minnesota, except paved
sections and a limited area in
northern and northeastern Minne
sota, are arbitrarily restricted by
law from March 20 to May 15 each
year to maximum weight limits of
four tons per axle. Administration
of the county and township restriction, however, does not lie with the
Highway department.
Generally unknown is the fact
that only about five per cent of all
traffic using Minnesota highways is
in any way affected by the restriction program. According to C. L.
Motl, chief maintenance engineer,
95 per cent of the traffic falls outside the restriction limits and
moves unimpeded the year-round.
Of trucks, alone, only about 25 to
30 per cent are affected.
With the help of ample advance
notice of approaching restrictions
from the Highway department,
many of the heavier truckers schedule added movement of heavier
loads before restrictions begin so
they are able later to comply with
the reduced load limits with a
minimum of difficulty.
Four major phases have marked
the Maintenance division's efforts
to meet the problem of springtime
breakup of the highways. Motl
summarized them as follows:
Here's what can happen to a Minnesota highway if excessive loads are permitted
on it in the spring breakup season. For a comparative test with restricted roads, the
highway shown, which was to be repaved in the summer, was excepted from its usual
springtime weight restriction. Roads which are not closed to heavier loads, as needed,
will close themselves to all traffic, light or heavy.
1.—Early day activity was
limited to repair of the damage,
with little, if any, preventive steps.
This was highly expensive in money
and effort greatly needed for new
construction and long-range maintenance. Many roads became impassable and could not be restored
to good travel condition until midsummer.
2.—The Highway department instituted and still continues an intensive study to determine the
definite cause of springtime road
damage. Though tjhe effect of
spring weather conditions was most
apparent in the road surfaces, the
cause was found to be temporary
weakening of the road base (earth
built up for the road foundation)
through freezing and thawing. The
weakened base allowed heavy traffic to break down surfacing materials, even occasionally including
concrete.
Restriction Started
3.—With enactment of necessary legislation, the highway department inaugurated a weight restriction program in which it bars
excessive loads from specified highways for the period during which
such loads would endanger the
roads.
The program includes periodic
advance notices of impending restrictions, distributed to newspapers, radio stations, and by direct mail to highway carriers and
carrier associations. Emergency
notices are issued when necessary.
Weight limits are posted on all
affected roads during the restriction
periods.
The state is divided into four
zones, the restriction periods moving chronologically by zones from
south   to   north.     Weight   limits
(Continued  on   page 6)