SUMMARY FACT SHEET HIGHWAY U.S. 89 - LOGAN CANYON STUDY
NOVEMBER 1986
Utah Department of Transportation (UOOT)
CH2M HILL Engineering Consultants
INTRODUCTION
UDOT has contracted with CH2M HILL for a study of US-89 in
Logan Canyon. The objective of the study is to evaluate
transportation needs, develop improvement alternatives and
to conduct an environmental evaluation of the alternative
concepts . Findings of each step of this study will be
reported to the public through a public involvement program,
of which this fact sheet is a part. Previously circulated
information about this study is available at the Logan
Public Library, Utah State University Library and Valley
Engineering in Logan; U.S. Forest Service in Ogden; and CH2M
HILL and UOOT offices in Salt Lake City.
The purpose of this fact sheet is to report the preliminary
findings of the first task of the study. A report on the
preliminary identification of public concerns/issues regarding
potential improvements to U.S. Highway 89 in Logan Canyon
from Right Hand Fork east to Garden City is also included.
Questions about the following information or the project in
general may also be directed to Gale Larson, Valley Engineering,
in Logan at 753-0153 or Cliff Forsgren, CH2M HILL, in
Salt Lake City at 363-0200.
REPORT ON TRANSPORTATION NEEDS
The first task of the study, the determination of transportation
needs on Highway 89 through the canyon, was to identify
existing roadway conditions; examine accident records for
the road; identify maintenance problems; identify traffic
volumes and characteristics; project future volumes; and
determine road capacity. The conclusions drawn from analyzing
this information include the location and nature of specific
highway safety hazards; the capability of the existing road
to carry present and future traffic volumes; and what problems
exist that may keep the highway from functioning at a
reasonable operational level. This information will be the
basis for the second task of the study, the development of
alternative improvements, if improvements are found to be
needed.
EXISTING ROADWAY CONDITIONS
Design conditions of the road that affect traffic flow include
cross-section elements, roadway curvature, roadway
gradient, and the width of and access to the highway rightof-
way. These are generally referred to as roadway geometrics.
Data for cross-section elements show the road section between
Right Fork and Tony Grove as being well below standard in
terms of width of traffic lanes, shoulders, surfacing slopes,
and ditches. The other sections, while below standard, are
not as seriously so.
Roadway curvature results in limited visibility and reduced
speeds. The curves of each road section were categorized by
their recommended speed. The section from Right Fork to
Tony Grove ranked highest in the number of curves and in
their severity, followed by the section from the Cache-Rich
County line to Garden City. Gradient describes how fast a
highway climbs or descends in elevation. The section from
Tony Grove to Garden City has gradients of 6 to 7 percent
over 31 percent of its distance. The majority of the road
from Logan to Tony Grove has gradients from 0 to 3 percent.
SAFETY ANALYSIS
The highway has been examined to identify specific locations,
or general conditions which may be contributing to traffic
accidents in the Canyon. To do this, the consultant examined
the number, type and location of accidents in the study section
from 1980 thrugh 1985. The hgihway was divided into 374 sections
of 0.10 mile each. The average number of accidents
per year for each section were then computed. Those sections
with significantly higher than average accident rates (accidents/
year) are being considered for safety related improvements.
There are 16 sections in this category.
MAINTENANCE FACTORS
Keeping the road open in winter is the single greatest maintenance
problem faced in Logan Canyon. In the narrower parts
of the canyon, there is nowhere to push the snow but into
the river. Where snow can be plowed to only one side of the
road, plows must move across both traffic lanes. This creates
a potential safety hazard, particularly when coupled with
low visibility due to curves and snow. Winds and steep slopes
in the canyon also create maintenance problems with drifting
and slides. Some flooding along the road occurs occasionally
during spring runoff.
TRAFFIC VOLUMES, CHARACTERISTICS, AND PROJECTIONS
Traffic volumes for Logan Canyon were obtained from the permanent
counting station located at Card Ranger ~tation from
1974 to 1983, and just west of Garden City from 1983 on.
Additionally, annual counts were taken at several points
within the canyon during 1986 to provide .ore detailed characteristics
of the traffic flow. Table 1 ahows the annual
average vehicles per day (AnT) and su~er average vehicles
per day on the road. Figure 1 shows the distribution of
traffic during the year, and Figure 2 shows the distribution
during the week.
Data collected from manual counts at the Right Fork intersection,
Tony Grove intersection, Reaver Mountain intersection,
and Summit (Sinks Road), showed:
o Variance in traffic volume between Right Fork and
Garden City,
o Distribution of traffic by direction of travel
(east/west)
o Composition of the traffic by vehicle type (car,
light truck, heavy truck)
Table 2 shows the variation in traffic volume over the entire
project route. It can be seen that in winter, counts at the
permanent station near the east end of the route were less
than half the volumes at the west end of the route (34 percent
and 44 percent). This indicates that there is/are substantial
traffic generators (origins/destinations) within
the canyon - Beaver Mountain ski area, cross-country skiing,
snow mobiling and other winter recreation destinations. The
summer volumes also show lower volumes on the east end than
on the west end of the route, (81 percent and 79 percent).
Since the summer time east end volumes are closer to west
end volumes than in winter, this suggests that recreation
within the canyon is less of a traffic generator in summer
than in winter. Most summer traffic in the Canyon is
through traffic.
Table 2
Because of economic and other considerations, highways are
normally not designed to accommodate the highest hours of
traffic volume during the year, which .ay happen infrequently,
but instead are designed for a lower volume hour that occurs
.ore often. UDOT nor.ally uses the 30th highest hourly volume
for the design hour volume (DIN). As is shown in Figure J,
the 30th highest volume hour for this study road segment is
consistent with hourly volumes immediately above and below
it, so little would be gained by choosing a different hourly
volume for the DIiV. The 30th highest hourly volume, about
14 percent of the average summer traffic, will therefore he
used as the hourly volume for which any improvements will be
designed.
Various techniques are used to project future traffic volumes.
All techniques rely on certain assumptions to provide the
basis of the forecast. This study selected a past trends
technique, which assumes that the trend established by past
changes in traffic volume will generally continue into the
future. Forecasts prepared using this method show an
increase in summer traffic volume of approximately
2 percent. The summer ADT in the year 2010 is projected to
be approximately 5800, a 75 percent increase over the
present. Figure 4 shows that these figures compare very
favorably to projections based on the current baseline
population projections for the Wasatch Front and Bear River
areas developed by the State of Utah. These areas are projected
to experience population increases averaging 1.95 percent
compounded annually. Using a projected annual growth
rate of 1.95 percent, the ADT in Logan Canyon at the Card
Guard Station would increase from 3,276 vehicles per day in
1980 to 5,847 vehicles per day in 2010. A summer ADT of
5,800 will therefore be used as the projected ADT for this
study.
Highway capacity analysis is the estimation of the maximum
amount of traffic that can be carried by a given length of
highway at various operational qualities. Six categories of
road operational quality are defined as Levels of Service
(LOS) "A" through "F", "A" being the best operational conditions,
F being the worst. Criteria for levels of service
address the freedom to move along a roadway without interference
from other vehicles. Once estimated; these road
capacities can be compared with existing and projected
traffic volumes to determine the current and future ability
of the road to carry the traffic.
The methodology used to analyze the traffic capacity of
U.S. 89 through the canyon is published in the Transportation
Research Board report, "Highway Capacity Manual, Special
Report 209." A "general terrain" methodology, which is based
on average terrain, geOMetrics and traffic conditions, vas
applied to the highway study aection. For conditions above
or below the average of these elements, the capacity was
increased or decreased. Under ideal operational conditions,
capacity for a two-lane road is 2,800 vehicles per hour (vph).
The results of the analysis are given in Table 4.
By comparing these capacities with the selected design hour
volume (DIN) based on present summer traffic volumes of
between 370 and 425 vehicles per hour (vph) and a OHV based
on projected summer traffic volumes of 545 to 627 vph, it
can be seen in Table 5 that the road is currently operating
during the summer at Level of Service D. By 2005, summer
operational conditions will have deteriorated in all segments
of the road to Level of Service E. This means that the road
is currently over its capacity to carry its traffic without
substantial delays occurring 75 percent or more of the time.
With future traffic volumes, delays on the road can be expected
more than 75 percent of the time.
CONCLUSIONS ABOUT TRANSPORTATION NEEDS
An examination of highway characteristics for the study section
of road suggests that the high number of curves resulting in
limited visibility, which prevents passing, and substandard
lane and shoulder widths are the greatest cause of the capacity
problem. The large proportion of recreational vehicles and
other slower vehicles of the total traffic volume is also a
significant contributor to the problem that may increase in
the future.
If it is desirable to accommodate present and projected
vehicle loads in Logan Canyon through the year 2010 at a
level of service higher than "OW or WE," it will be necessary
to improve problem areas of the roadway in some manner.
This can best be accomplished by increasing passing opportunities
and widening traffic lanes and shoulders, thus
helping to prevent the formation of vehicle platoons and
allowing traffic to move more freely through the canyon.
Specific methods of achieving these improvements will be
developed in the next step of the study, the development of
improvement alternatives.
PRELIMINARY REPORT ON ENVIRONMENTAL ISSUES AND CONCERNS
On August 26, the environmental and engineering staff of
CH2M HILL working on the Logan Canyon project toured the
Highway 89 study section with representatives of various
local enviro~ntal groups and the U.S. Forest Service. The
purpose of the tour was for the engineering consultant to
gain a preliminary understanding of what environmental issues
and concerns need to be considered in the development of
improvement plans for the canyon.
The following s\l~ary of the findings is preliminary because
other opportunit1es for public input regardi.ng environmental
concerns will occur prior to the selection of the preferred
improvement alternatives and prior to the environmental analysis
of the project. Nevertheless, it is important for the
consultant to be aware, prior to any development of improvement
alternatives, what are considered to be the most important
and sensitive environmental resources of the canyon.
During the tour, it was suggested by some present that the
Canyon should be treated as a recreational corridor (a destination)
rather than as a transportation link (a conduit
for traffic). Recreational use of the corridor should be
given priority over transportation use whenever a decision
involving trade-offs is to be made in the study. Recreational
use . d~a~s with visual resources, fishery habitat, recreational
facilities, vegetation, and possibly other environmental
elements.
It was also pointed out that a special ambience exists in
the lower part of the study route (Right Fork to below Lower
Twin Bridge), created by the narrm" canyon walls, sheer rock
cliffs, and tree canopy. Although the existing highway has
been constructed through the canyon, other signs of human
alteration are minimal. A number of specific elements that
contribute to this overall ambience were identified.
o Visual concern regarding road cuts and fills;
destruction of focal points and existing fields of
view; introduction of artificial features; imposition
of human alterations upon a relatively natura).
setting
o Recreation - protection of campgrounds, picnic
areas and features of interest (springs, caves,
etc.); provision of necessary facilities at interest
points (parking, restrooms, etc.); bicycle
safety; protection of fisheries
o River Protection - as a visual element; as a water
body; as fishery habitat; as a recreational resource
The tour progressed through the canyon from Logan to Bear
Lake viewpoint with stops among the way to address specific
concerns at sensitve locations where road improvements were
proposed in the past. The area from Right Fork to Tony Grove,
the summit, and the Bear Lake viewpoint are the locations on
the route that are most sensitive.
Concern was cited that slopes in the lower canyon are so
steep that cuts for the purpose of road widening can result
in serious slope instability and slides. Avalanches can
also be a problem in winter. Installation of guardrails in
some places on the road has decreased site distance, cutting
utilization of the few good passing locations. In other
locations, their installation has eliminated views of the
river.
As additional concerns and issues relating to possible road
improvements in the canyon become identified, they will be
reported in project fact sheets, press releases, and public
meetings.
