HomeMy WebLinkAboutCDOT POUDRE RIVER REST AREA - SITE PLAN ADVISORY REVIEW - 27-04 - REPORTS - TRAFFIC STUDYor TIS FOR THE REL, .ATION OF THE CDOT
POUDRE RIVER REST ARE
connected (sometimes even operated from a single controller); so the southbound ramp
terminal should also be signalized.
■ Frontage Road Signalization. The intersection of the Western Frontage Road and Prospect
Road also needs to be signalized.
■ Ramp terminal geometrics. The northbound approach of the ramp terminal should be re -
striped to provide channelization for a left turn lane — allowing through and right turning traffic
to have their own lanes.
■ Westbound approach at the Western Frontage Road. The relocated rest area will be adding
up to 86 vehicles in the peak hour making a left turn from westbound Prospect to the Frontage
Road. This volume meets warrants for a left turn lane and it should be designed to
accommodate the higher than typical truck volumes.
■ Pavement improvement along Prospect and Frontage Road. As a part of final design, a
geotechnical investigation of the existing roadways should take place, and any necessary
pavement improvements be accomplished.
2. SUMMARY
. With these improvements, the Poudre River Rest Area will be allowing not only adequate access for itself,
but will be providing substantial improvements to current users of the roadways. The lengthy delays and
safety issues related to limited sight distance at the northbound ramp terminal will be significantly reduced.
With these improvements, the interchange is expected to function adequately for the next 8-10 years.
In the 20-year time horizon, due to regional growth, the volumes on the Prospect Road overpass exceed
the capacity of a two-lane facility. The inability to provide for auxiliary turn lanes from Prospect onto the I-
25 ramps over the bridge, as well as the need for double left turn lane northbound is the limiting factor.
This constraint will be present with or without the rest area.
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In the 20-year horizon, even with signals, both the Southbound and Northbound 1-25 ramp terminals
have failing levels of service. The constraining factor is the lack of auxiliary lanes over the bridge for
left turning vehicles. This requires through moving vehicles to back up, and with high through volumes,
the capacity is no longer available to accomplish acceptable levels of service. In addition, the
northbound off ramp left turning volume is more than 1200 vehicles. This absolutely requires a double
left turn lane (which is not possible with only one lane over the bridge). The volumes are shown in
Figure 13, and the Levels of Service are shown in Figures 14 and 15. Assumed geometrics are shown
in Figure 17.
Bottom Line: For a traditional signalized intersection, the bridge needs to be widened in order to
achieve an acceptable Level of Service. This result occurs with or without the rest area traffic.
2. PEDESTRIAN, BICYCLE AND TRANSIT LEVEL OF SERVICE ANALYSIS
The intent and purpose of an interstate rest area is to accommodate vehicular traffic utilizing the interstate.
Pedestrians, bicycles, and transit modes outside the site are not a part of this study. However, a number of
improvements will be realized by multi -modal users:
■ The site plan for the rest area is designed for the internal circulation of pedestrians, especially
between the rest area and the welcome center;
■ The new bridge over the Box Elder Creek will have a sidewalk,
• The off -site roadway improvements will provide a widened shoulder for improved bicycle
usage;
• The three signals to be installed will provide positive direction for all users when it is
appropriate to enter the intersection.
CL STUDY CONCLUSIONS AND RECOMMENDATIONS
The existing Prospect Road interchange has two intersections that currently meet multiple signal warrants.
The Western Frontage Road sees high levels of through traffic and unacceptable delays for minor street
traffic. The 1-25 southbound ramp has very long delays and queues are beginning to impede on mainline
traffic.
Relocating the Poudre River Rest Area to the Prospect Road interchange will typically increase the traffic
volume at the intersections by 2-3 % in the morning and 7-8% in the evening in all time horizons (the
eastern Frontage Road intersection remains only nominally affected by the Rest Area relocation). This
difference, although occasionally affecting an intersection by one LOS, is not enough to substantially affect
the interchange function. Therefore, whether the interchange functions adequately or not is
overwhelmingly determined by the background traffic and not the proposed rest area traffic.
1. OFF -SITE IMPROVEMENTS RECOMMENDED
Despite a relatively low level of impact that the rest area will have on the traffic volumes, due to existing
deficiencies, there are a number of off -site roadway improvements necessary prior to the opening of the
Relocated Poudre River Rest Area:
■ Ramp Terminal Signalization. The northbound ramp terminal needs to be signalized prior to
any additional development traffic. Ramp terminal intersection controls are generally
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The assignment of the site traffic will vary at each horizon due to the growth of the rest area traffic. The
2005, 10-year, and 20-year traffic assignment is shown in Figure 7, 10, and 13, respectively.
Truck Volumes
Truck volumes within the traffic assignment were identified and used to specifically calculate truck
volumes for each turning movement in each time horizon. This should provide a realistic look at how
trucks utilizing the rest area will affect the interchange. Truck volumes vary from as low as 3% (due to
high volume of car traffic) to 15% for some specific interchange turning movements. The intersection
at the Western Frontage Road has some movements with truck percentages as high as 50% (the
northbound right turn in the AM).
D. BACKGROUND TRAFFIC PROJECTIONS
Background traffic is that traffic that will be utilizing area roadways without the addition of the proposed site
traffic. In order for the analysis of future year time horizons to be accurate, the traffic volumes used needs
to include an assumed amount of growth in the background traffic.
The growth rate of traffic using the rest area was discussed in Section CA. The growth of existing traffic at
the Prospect Road Interchange was calculated separately. Five sources were used to gather potential
growth information:
• CDOT growth factors for 1-25 mainline (which vary from 1.5 to 3.0 in the area),
■ The City of Fort Collins travel demand model (updated for the Mason Street Corridor and Mulberry
Study),
■ The MPOs travel demand model for traffic anticipated east of 1-25,
■ 1-25 Corridor Plan completed as a multi -jurisdictional document, and
• Recent Traffic Impact Studies for development in the area.
It is clear that the likely growth throughout the corridor will vary substantially by location within the study
area. For example, the Prospect corridor west of the interchange has 18,000 vehicles per day and a
typical growth rate of 3.5% per year is anticipated by most sources. The current average daily traffic along
Prospect east of the interchange is only 2,300 vehicles per day and 20-year estimates vary from 9,000 —
14,000 vpd. A growth rate of over 7% (resulting in a 20-year factor of 4.0) seems more reasonable for this
section of roadway.
In this manner, each section of roadway was studied independently, the sources reviewed, and an annual
growth rate identified for that approach volume. 20-year growth factors resulting from the growth rates are
shown in Figure 6.
Growth Factors
3.0
d
/Yq 2.0 4.(7. F
3 z
(3.5%.Nr)
2.0 2.0 4.0
(3.5WYr) (3.5%Nr) (7.2%No
E. wmn.n as
3.
(5. //(3 2.0 20r)
(5.6%dYr) (35%nr).5%dY
20 Year
X.X Growth Factor
( X.X%(Yr) Growth Rate I Year
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Figure 6 — 20-Year Growth Factors for Background Traffic
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-,,_:�_ POUDRE RIVER REST ARE
5. PEDESTRIAN, BICYCLE AND TRANSIT FACILITIES
The project site is in an undeveloped more rural area. There are no current pedestrian facilities along the
Western Frontage Road, Prospect Road, and pedestrians are not allowed on 1-25. Bicycles within the
project study limits are currently utilizing the roadway shoulders. There are no transit accommodations in
the area.
C. PROPOSED DEVELOPMENT / SITE GENERATED TRAFFIC
The proposed development is an interstate rest area whose purpose is to provide motor vehicles utilizing I-
25 with a place to stop, rest, use facilities, and have access to the neighboring welcome center.
1. TRIP GENERATION
Site generated traffic in this study is the estimated traffic that will be in the area due to the relocation of the
rest area. For the immediate timeframe, that traffic is assumed to be the same as the existing traffic at the
Poudre River Rest Area as shown in Table 1.
Unlike many standards traffic studies, the site -generated traffic will experience growth over time; this
growth is directly related to the anticipated growth of traffic on 1-25. CDOT estimates an annual growth of
3.53% along the mainline (both cars and trucks). Therefore, the site traffic used in the analysis is based
upon the numbers shown in Table 1 and the applicable amount of growth added. This results in the
following multipliers:
Year Factor
2005 1.11
10 yr 1.41
20 yr 2.0
2. TRIP DISTRIBUTION AND ASSIGNMENT
The trip distribution is assumed to be similar as that currently using the Poudre River Rest Area. Because
the existing sites have separate northbound and southbound facilities, it is easy to determine the current
distribution: fifty-five percent of the use is from northbound 1-25 and forty-five percent is from southbound
traffic. How this distribution relates to the Prospect Road interchange is shown graphically in Figure 5.
Trip DMblbubon
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Figure 5 —Site Traffic Trip Distribution
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Synchro analysis printout sheets are included in Appendix D, and the details of the signal warrant
analysis are included in Appendix H. Signalization warrants were completed using the MUTCD, Part 4,
Highway Traffic Signals, 2000. A summary of the existing traffic operations is shown below:
Western Frontage Road: Currently functioning at an overall LOS A in both the morning and evening.
However, the Frontage Road approaches are both at a LOS F with long delays. This intersection
currently meets the following signal warrants:
■ Warrant 1 — 8-Hour Vehicular Volume
■ Warrant 2 — 4-Hour Vehicular Volume
■ Warrant 3 — Peak Hour Vehicular Volume
Adding a traffic signal at the Western Frontage Road intersection would improve the function to an
overall LOS A and the Frontage Road approach improves from LOS F to LOS C and B (northbound
and southbound).
1-25 southbound ramp: Functioning well with limited delay and queue lengths.
1-25 northbound ramp: This intersection has an overall LOS F in both the morning and evening peak
hours. The morning delay for traffic exiting the interstate averages over three minutes (the limit for
LOS F is only 50 seconds). The queue lengths on the ramp are beginning to impede onto the 1-25
mainline. This intersection currently meets the following signal warrants:
• Warrant 1 — 8-Hour Vehicular Volume
■ Warrant 2 — 4-Hour Vehicular Volume
■ Warrant 3 — Peak Hour Vehicular Volume
Adding a traffic signal at the 1-25 northbound ramp intersection would improve the function to a LOS B.
Eastern Frontage Road: Functioning well with limited delay and queue lengths.
Accident Data at the Interchange
Accident data for the Prospect Road Interchange was obtained from CDOT's Accident Data
Management Team within the State's Safety office. The raw data is included in Appendix I and
contains three years of accident data from January 1, 1999 to December 31, 2001. (The City of Fort
Collins was also contacted — they have only one year of data available that included a couple additional
accidents at the interchange not listed in CDOT's information.) There were 36 accidents in the area
during the three-year time period, of which 29 were related to the interchange.
The largest percentage of accidents (62%) were
related to the northbound off ramp and ramp terminal.
Only 34% were related to the southbound ramps.
There may be two contributing factors to the higher
accident occurrence for northbound vehicles: the
limited sight distance makes the margin for error
smaller than at most intersections (see photo at right),
and the current long queues and delays tend to
encourage drivers to accept a smaller gap than typical.
Signalization of the intersection at the northbound
ramp terminal would eliminate the requirement of the
driver decision in choosing a gap, and would reduce
the delays by increasing capacity of the intersection.
Northbound Ramp Terminal Looking West
(limited site distance)
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The other set of traffic counts completed were peak hour turning movement counts at the ramp
terminals, and the east and west frontage roads. Counts were completed over a two-hour period in
both the morning and evening (7:00 — 9:00 a.m. and 4:00 — 6:00 p.m.). The peak hour was determined
to be 7:15 — 8:15 a.m. and 4:45 — 5:45 p.m, and the data was minimally balanced between
intersections since the counts were not all completed on the same day. These two time frames will be
used for all analysis. The existing traffic is shown in Figure 4.
4. EXISTING MOTOR VEHICLE OPERATIONS
Current Traffic Operations
Traffic analysis is based upon a Level of Service analysis as outlined in the Highway Capacity Manual
(HCM 2000) published by the Transportation Research Board (TRB). This type of analysis assigns a
letter value to an intersection, approach or movement based on average delay experienced by vehicles
utilizing that intersection, approach or movement. The letter values assigned range from A (the best)
to F (the worst). Table 2 summarizes the definition of different LOS for signalized and unsignalized
intersections.
Table 2 — Summary
of Level of Service Information
Signalized Intersection
LOS Delaysec/veh)
Unsignalized
Intersection
LOS Dela sec/veh
Definition
A
<10.0
A
<-10.0
Favorable progression _
B
>10.0 and <_ 20.0
B
>10.0 and <— 15.0
Good progression _
C
>20.0 and <_ 35.0
C
>15.0 and < 5
Fair progression
D
>35.0 and <_ 55.0
D
>25.0 and
congestion
E
>55.0 and <_ 80.0
E
>35.0 and E_ff
E�,J_ceable
mt of acceptable delay
F
>80
F
>50
Approaching Unacceptable
Source: Hichwav Capacity Manual, Transportation Research Board 2000
The acceptable delays between signalized and unsignalized intersections are different for like levels of
service because drivers generally have a different expectation of delay at the two intersections.
Drivers approaching a red light expect to be delayed. Drivers approaching a stop sign expect to stop
and then move on.
In larger urban areas, it is standard engineering practice to assume that a facility with LOS A through
LOS D is within an acceptable range for most users. For Prospect Road in the City of Fort Collins, an
overall LOS D is the limit of acceptable delay at a signalized intersection. For unsignalized
intersections, an overall LOS F is acceptable and considered normal in an urban environment.
Capacity improvements to stop controlled intersections often means the addition of a traffic signal. The
need for a traffic signal is based upon ITE's 2001 Manual of Uniforn Traffic Control Devices which
details eight Warrants and their requirements. An intersection needs to meet one or more of the eight
warrants before being considered for a signal.
The traffic analysis was completed using the Synchro software program. This program utilizes the
accepted methods of analysis as detailed in the HCM. It also can optimize timing plans, and it
incorporates the various intersections' effects on one another. Figure 4 shows the existing operations,
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Information from the CDOT traffic database was obtained to determine the seasonal variation of traffic
along 1-25, and the appropriate factors to apply to both cars and trucks to estimate peak month travel.
Truck traffic remains steady throughout the year, and the numbers obtained in April can be used in the
analysis. Car traffic peaks in August and the adjustment factor between our April data and August data
is 1.2.
Using the above information, existing rest area traffic likely to occur in August during the peak travel
time is shown in Table 1.
Table 1
2002 Peak Hour Rest Area Traffic
(Adjusted to August)
Southbound Northbound
Cars Trucks Cars Trucks
AM Peak Hour 5 8 6 8
7:15-8:15a.m.
PM Peak Hour 29 6 36 6
4:45 — 5:45 .m.) i
Accident Data at the Existino Rest Area
Accident data for the existing rest area location was obtained from CDOT's Accident Data
Management Team within the State's Safety office. The raw data is included in Appendix I and
contains three years of accident data from January 1, 1999 to December 31, 2001. There were 33
accidents related to the rest area site, of which 22 were northbound accidents and 11 were southbound
accidents. 40% of the accidents were sideswipes or rear -ends while 33% involved some sort of fixed
object. There is no specific type of accident highlighted as an area of concern. The higher rate of
northbound accidents may be attributed to the uphill acceleration required as trucks enter the freeway
from the rest area.
Traffic Volumes at Existing Prospect Road Interchange
Two sets of existing traffic counts were completed in the interchange area for this study. 24-hour tube
counts in 14 locations were done to determine directional ADTs (Average Daily Traffic) on the ramps
(four counts), frontage roads north and south of Prospect (8 counts), and Prospect Road (2 counts).
The tube counts provided hourly volumes that were used in the signal warrant analysis. A summary of
the average daily traffic in the study area is shown in figure 3.
ADT - Average Daily Tnttic
u y a z ,wnn
2,100 e i
1,800 350
vehlday2,00
veh/da0y vehlday vehlday
C / 2,200
i veh/tlav
E. R... Rc
18,600
vehlday
8 4 250
950
veh/day 6,700 6,450 veNtlav
3 V veh/day veh/dav
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fFigure 3 — Existing Average Daily Traffic (ADTs)
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The travelway over the bridge is a narrow 26 ft. The only existing auxiliary turn lane is a free right from the
southbound off ramp to westbound Prospect (see aerial above). There is limited sight distance for vehicles
at the northbound off ramp.
All intersections in the study area are stop controlled.
3. EXISTING TRAFFIC VOLUMES AND CONDITIONS
Traffic Volumes at Existing Rest Area
Contacts were made to the Region 4 traffic engineer, Region 4 Maintenance Personnel, and the
Poudre River Rest Area Caretaker to discuss current rest area traffic. The caretaker identified Friday —
Sunday as the peak traffic time (both cars and trucks) at the rest areas. Since weekday traffic is of
greatest interest to the potential relocation (as the Prospect Road Interchange peaks are on
weekdays), 72-hour classification tube counts at the entrance and exits of the facilities were completed
April 4-6 2002. This determined how many vehicles are currently accessing the facilities, and what the
anticipated trip generation would likely be when the rest area is moved. In addition, a 24- hour
occupancy study was also completed on Friday, April 51". This identified how many vehicles are at the
facilities at a time and will help determine the amount of parking needed at the new facility. Raw data
is included in Appendix C.
Figure 2 shows the existing traffic entering the rest areas. It is important to note that peak incoming
traffic hours at the rest area are 11:00 a.m. - 12:00 noon and 3:00 — 4:00 p.m. These do not coincide
with the peak travel hours at the Prospect Road Interchange, (which occur at 7:15 — 8:15 a.m. and 4:45
— 5:45 p.m.).
Existing Traffic Entering Rest Area
(sum of northbound and southbound)
Aoril 2002
Prospect Road
100
90
80
70
60
50
40
30
20
10
0
1:00 4:00 7:00 10:00 13:00 16:00 19:00 22:00
Time
Figure 2 - Existing Rest Area Traffic
■ trucks
Bear
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B. EXISTING CONDITIONS
1. LAND USE
The project site is located just south of the existing Colorado Welcome Center. The 15-acre piece of
property is undeveloped. A portion of the site was mined by LaFarge, and final grading of extensively
disturbed ground has only recently taken place.
In the area around the site, there is currently limited development, and the area appears quite rural. The
immediate area surrounding the interchange is predominantly zoned for commercial uses. There has been
substantial discussion about growth in the area, including the potential for:
• The redevelopment of the Resource Recovery Farm (south west corner of the interchange),
• A new high school east of 1-25 and north of Prospect,
• Larger retail center(s) east of the interchange
• Continued regional growth of close -by communities such as Windsor and Timnath. While
these communities typically use neighboring interchanges, their growth will likely add some
traffic to the interchange at Prospect Road
2. AREA ROADWAYS
The site is adjacent to the Western Frontage Road of 1-25. This roadway is an existing two-lane facility
with narrow shoulders. It is quite rural in nature with limited improvements (no curb and gutter or
sidewalks).
Prospect Road is within the City of Fort Collins city limits when it intersects with the Frontage Road and
designated as a four -lane arterial from the west to the northbound ramp terminal of 1-25. Its current
configuration is as a two-lane facility with limited improvements (no curb and gutter or sidewalks). From
the northbound ramp terminal to the east, Prospect Road is designated as a minor 2-lane arterial.
The interchange at 1-25 and Prospect Road is at Milepost 268.5. The interchange is a typical diamond with
stop controlled ramp terminals on either side of the Prospect Road overpass. The ramp terminals are 550
It apart with both east and west -side frontage roads 1050 ft on either side of the ramp terminal
intersections.
Prospect Road Interchange
(source: City of Fort Collins GIS)
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Relocation of the
Colorado Department of Transportation
Poudre River Rest Area
O O a
July 9, 2004
Completed for:
or Colorado Department of Transportation
Submitted to:
City of Fort Collins
Sear -Brown Projects 813-005, 813-007
Stantec Projects 181700036
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