HomeMy WebLinkAbout1.04 April 14 Skylark School Level Two Traffic Study (2)April 14, 2014
Daniel Roussin
State of Colorado Department of Transportation
Region 3 Traffic Section
222 S. Sixth St., Room 100
Grand Junction, Colorado 81501
Re:Skylark School – Mountain View Church Site
Level Two Traffic Study – Access Permit Request
CR-154 / SH-82 Intersection, Glenwood Springs/Garfield County, Colorado
Dear Mr. Roussin:
Per State of Colorado Department of Transportation (CDOT) requirements, this
study presents the results of a Level Two trip generation and auxiliary turn lane
improvement identification for Skylark School. Skylark School is proposing to
build a school as an addition to existing Mountain View Church. The church is
located on the south and west side of CR-154, with its property line
approximately 200 feet from the SH-182 intersection in unincorporated Garfield
County, near Glenwood Springs, Colorado. The church has access to CR-154 in
two locations, near its north and south property lines. This traffic impact study
provides an evaluation of the SH-82/CR-154 intersection for purposes of
obtaining an access permit for the addition of a school to the existing church.
Skylark School has a proposed enrollment of 108 students for grades K-12.
Analysis was completed for the 2015 design year horizon as well as the 2034
twenty year horizon for purposes of this study with an access permit.Figure 1
illustrates the vicinity of Skylark School at Mountain View Church with respect to
the surrounding area and Glenwood Springs.
There are currently two access driveways for the Mountain View Church
property. It is understood that the Church has elected to close the southernmost
access driveway, closest to the SH-82/CR-154 intersection. The Church will also
dedicate right-of-way as necessary to allow for the realignment of CR-154 as
CDOT has proposed. An image showing the conceptual geometry for the
realignment was provided by CDOT for inclusion in this letter (see following
image). This access realignment will improve separation for the mobile home
access to the south. Coordination for this CR-154 realignment is necessary
through the Buffalo Valley site as well as the mobile home parcel. Skylark School
and Mountain View Church are proposing all possible with respect to these
improvements.
n
Suite 200
990 South Broadway
Denver, Colorado
80209
n
TEL 303 228 2300
Mr. Daniel Roussin, March 21, 2014, Page 2
Conceptual Geometry for Proposed CR-154 Realignment
(Image provided by CDOT in April 2014)
SH-82 is a CDOT maintained highway with an access control category of
Expressway, Major Bypass (E-X). The roadway has a posted speed limit of 55
miles per hour, although it is identified as a 65 mph roadway in CDOT OTIS. The
highway is undivided with two lanes in each direction through the intersection
with CR-154. The CR-154/SH-82 intersection operates with a traffic signal. The
SH-82 southeastbound approach to CR-154 contains designated left and right
turn lanes. The SH-82 northwestbound approach to this intersection contains a
designated left turn lane. The CR-154 approach to the intersection contains one
approach lane for all movements. The southwestbound approach is unpaved and
on private property.Figure 2 illustrates the intersection lanes and control of the
existing intersection.
It is understood that CDOT is considering future improvements to the CR-154 and
SH-82 intersection. These improvements include removal of the private access
leg on the northwest side of the intersection. In addition, the existing traffic
signal would be removed. Due to the speed of the highway, we believe it would
be optimal in that condition to restrict movements at the intersection to three-
quarter, with the CR-154 approach left turn onto northwestbound SH-82
restricted. This shouldn’t be an issue as street connectivity exists for CR-154 into
Glenwood Springs to the north. Likewise, this will reduce the queue of traffic on
the approach to SH-82 with a right turn movement. As part of these
improvements, CDOT should consider the construction of an acceleration lane
along southeastbound SH-82. This lane is warranted based on existing traffic. If
a free right turn movement were constructed along with the left turn exit
restricted, the CR-154 approach to the intersection would operate with free
Mr. Daniel Roussin, March 21, 2014, Page 3
movements and no queue. For purposes of this study, the existing intersection
configuration was considered to provide a conservative analysis.
Existing peak hour turning movement counts were conducted at the key
intersections on Wednesday, November 20, 2013. The counts were obtained
during the morning and afternoon peak hours of adjacent street traffic in 15-
minute intervals from 7:00 AM to 9:00 AM and 4:00 PM to 6:00 PM, respectively.
The attached Figure 3 illustrates the existing traffic volume counts (data sheets
are also attached).
According to information provided on the CDOT website, SH-82 carried
approximately 21,000 vehicles per day in 2012. The 20-year growth factor along
this segment of the highway, 1.47, equates to an annual growth rate of 1.94
percent per year. This annual traffic growth was applied to the existing 2013
movements along SH-82 at the intersection to obtain future 2015 and 2034
background traffic volumes. In addition, project traffic volumes anticipated at
the CR-154 and SH-82 intersection were applied directly per the “Buffalo Valley
Apartments Traffic Impact Study”, prepared by Kimley-Horn and Associates, Inc.
in December 2013. The projected future 2015 and 2034 background traffic
volumes without Skylark School are shown in attached Figures 4 and 5.
Site-generated traffic estimates are determined through a process known as trip
generation. Rates and equations are applied to the proposed land use to
estimate traffic generated by the development during a specific time interval.
The acknowledged source for trip generation rates is the Trip Generation Report1
published by the Institute of Transportation Engineers (ITE). ITE has established
trip rates in nationwide studies of similar land uses. For this study, Kimley-Horn
used the ITE Trip Generation Report regression equations that apply to Private
School K-8 (534), using ITE’s Recommended Procedure for Estimating Trip
Generation methodology. The K-8 was used instead of K-12 for several reasons.
The first was that the size of the Skylark School was not within the data bounds of
the K-12 trip generation chart. There were also not enough data points to suggest
using the average rate of that use. The final reason for using the K-8 instead of K-
12 was that the K-8 offered a more conservative estimate than the K-12 Private
School.
Using the ITE Trip Generation Manual and the Private School (K-8) use, the
anticipated trips generated by the addition of the Skylark School were
determined. The following table summarizes the estimated trip generation for
the 108-student proposed Skylark School. These volumes, as well as all volumes
in this letter, are reported in passenger car equivalents (PCEs).
1 Institute of Transportation Engineers,Trip Generation: An Information Report, Eighth
Edition, Washington DC, 2008.
Mr. Daniel Roussin, March 21, 2014, Page 4
Trip Generation for Skylark School
Land Use Vehicle Trips
Size
(students)
Weekday AM Peak
Hour of School
Weekday PM Peak Hour
of School
Project In Out Total In Out Total
Skylark School 108 55 45 100 29 32 61
Distribution of school traffic on the adjacent roadways and through the key
intersection was based on the area street system characteristics, existing traffic
patterns and surrounding residential areas. More specifically, the distribution
was determined based on the future student’s home addresses since traffic
to/from the school will generally originate and terminate at the student’s home
address. The directional distribution of traffic is a means to quantify the
percentage of site-generated traffic that approaches the site from a given
direction and departs the site back to the original source direction. Attached
Figure 6 illustrates the Skylark School trip distribution. The trip generation
described previously was multiplied by the trip distribution developed to
determine the project traffic assignment shown in Figure 7. The project traffic
assignment was added to the 2015 and 2034 background traffic volumes to
determine the total traffic with Skylark School, as shown in attached Figures 8
and 9.
Based on the traffic assignment, the auxiliary turn lane requirements were
calculated based on the State of Colorado State Highway Access Code (SHAC) for
the SH-82 and CR-154 intersection. According to the State Highway Access Code
for category E-X roadways with a 55 mile per hour speed limit, the following
thresholds apply:
·A left turn deceleration lane and taper with storage length is required for
any access with a projected peak hour ingress turning volume greater
than 10 vph. The taper length is to be included in addition to the required
deceleration length.
·A right turn deceleration lane plus taper is required for any access with a
projected peak hour ingress turning volume greater than 10 vph. The
taper length is included in addition to the required deceleration length.
·A right turn acceleration lane plus taper is required for any access with a
projected peak hour right turning volume greater than 10 vph. The taper
length is to be included in addition to the required acceleration length.
Based on these thresholds from the SHAC, all possible auxiliary turn lanes are
warranted at the SH-82 and CR-154 intersection based on existing traffic
volumes. The following turn lane improvements are warranted at the SH-82 and
CR-154 intersection:
Mr. Daniel Roussin, March 21, 2014, Page 5
·A westbound to southbound left turn deceleration lane along SH-82 is
warranted today based on existing traffic volumes during both the morning
(16 vph) and afternoon (40 vph) peak hours having traffic volumes greater
than the warrant threshold of 10 vph. Based on the SHAC, this lane should
provide deceleration, plus storage, plus taper length. The left turn traffic
volume is projected to be 63 vehicles per hour in 2034, so 75 feet of storage
length is required. The deceleration length is 600 feet, plus the 18.5 to 1 bay
taper based on the 55 mile per hour speed limit of SH-82 through this
intersection. Therefore, per the SHAC, this lane should provide a left turn
lane length of 675 feet plus a 225-foot bay taper. This left turn lane exists
today and has been constructed at a length of approximately 350 feet with a
120-foot bay taper. It is believed that lengthening this left turn lane is not
feasible or desirable since it has been designated as a back-to-back left turn
lane for the eastbound left at Red Canyon Road intersection further to the
southeast.
·An eastbound to southbound right turn deceleration lane is warranted
today based on existing morning (15 vph) and afternoon (16 vph) peak hour
traffic exceeding the warrant volume threshold of 10 vph. Based on the
SHAC, this lane should provide deceleration plus taper length. The
deceleration length is 600 feet, plus the 18.5 to 1 bay taper based on the
posted 55 mile per hour speed limit of SH-82 through this intersection.
Therefore, per the SHAC, this lane should provide a right turn lane length of
600 feet plus a 225-foot bay taper. This right turn deceleration lane exists
today with a length of approximately 250 feet plus a 200-foot bay taper.
Therefore, the existing lane does not meet current SHAC standards. It is
believed that this right turn deceleration lane length may have been
constructed at the existing length due to a pullout that exists along
eastbound SH-82 approximately 450 feet west of the SH-82 and CR-154
intersection.
·An eastbound acceleration lane along SH-82 for right turning traffic from CR-
154 is warranted based on existing traffic and SHAC thresholds. The
morning peak hour right turn volume is 43 vph and the afternoon peak hour
right turn volume is 27 vph, which are both greater than the 10 vph
threshold volume. A right turn acceleration lane along eastbound SH-82 at
this CR-154 intersection has not been constructed, although warranted
based on existing traffic volumes. It is possible that the requirement was
waived by CDOT due to constraints. There are many issues adjacent to SH-
82 south of the CR-154 intersection including grade, the trail, and right-of-
way. If it were feasible to be constructed, an acceleration lane length of 960
feet plus a 225-foot taper would be required to meet SHAC requirements.
However, an access to Holy Cross Energy is located approximately 700 feet
east of the SH-82 and CR-154 intersection. So, if this acceleration lane were
constructed, it is believed that it would be a combination acceleration/
deceleration lane between CR-154 and the Holy Cross Energy access along
Mr. Daniel Roussin, March 21, 2014, Page 6
eastbound SH-82. Of note, it is believed that if traffic volume counts were
conducted at the SH-82 and Holy Cross Energy access, a right turn
deceleration lane may be warranted as well. Instead of construction of an
acceleration lane, posting the CR-154 approach to “NO RIGHT TURN ON
RED” would alleviate the concern of traffic turning right into the through
lanes of SH-82 traffic traveling at 55 mph during the SH-82 green phase.
Based on the addition of Skylark School project traffic, it is believed that CDOT
will require an Access Permit Application for the CR-154/SH-82 intersection due
to the school increasing traffic at the intersection by more than 20 percent. It is
recommended that CDOT consider the construction of an eastbound acceleration
lane along SH-82 at this intersection. This lane is warranted today based on
existing traffic, so it isn’t something that should be required of the school to
construct. Therefore, it is likely that CDOT will require a design waiver be
submitted for this improvement as well. Since it is believed that construction of
this right turn acceleration lane is not feasible, it is recommended that a “NO
RIGHT TURN ON RED” sign be installed for the CR-154 approach to SH-82.
This information is provided to you for your consideration in issuing access
permits for the use of Skylark School. If you have any questions relating to this
analysis, or require anything further please call me at (303) 228-2300.
Sincerely,
KIMLEY-HORN AND ASSOCIATES, INC.
Curtis D. Rowe, P.E., PTOE
Vice President
Attachments
4/14/14
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Project Skylark School
Subject Trip Generation for Private School (K-8)
Designed by SES Date April 14, 2014 Job No.
Checked by Curtis Rowe Sheet No.1 of 1
TRIP GENERATION MANUAL TECHNIQUES
ITE Trip Generation Manual 9th Edition
Land Use Code - Private School (K-8), (534)
Independant Variable - Students (X)
X = 108
T =Average Vehicle Trip Ends
A.M. Peak Hour (page 1030), Fitted Curve
Directional Distribution:55%ent. 45%exit.
Ln(T) = 0.90 (X) + 3.01 T =100 Average Vehicle Trip Ends
Ln(T) = 0.90 * 108 +3.01 55 entering 45 exiting
55 +=100
P.M. Peak Hour of Generator (page 1031), Fitted Curve
Directional Distribution:47%ent. 53%exit.
Ln(T) = 0.61 (X) - 4.70 T =61 Average Vehicle Trip Ends
Ln(T) = 0.61 * 108 - 4.70 29 entering 32 exiting
29 + =61
45
32