4.10. SR 01-20-2015City of
Elk
River
Request for Action
To
Item Number
Mayor and City Council
4.10
Agenda Section
Meeting Date
Prepared by
Consent
January 20, 2015
Justin Femrite, P.E., City Engineer
Item Description
Reviewed by
Twin Lakes Road —171st Avenue Intersection
Cal Portner, City Administrator
Analysis
Reviewed by
Action Requested
Approve, by motion, the preliminary design of a traditional T- intersection at Twin Lakes Road and 171"
Avenue.
Background /Discussion
At the October 20, 2014, meeting, Council directed staff to work with the area stakeholders to analyze
alternative options for the future intersection of Twin Lakes Road and 171" Avenue. The conceptual idea
included in the 171" Area Focused Area Study (FAST) identified the use of a roundabout at this
intersection. Since the October meeting, staff has met on two separate occasions with representatives
from Lefebvre Companies, Morrell Companies, Novco, and Preferred Powder Coating, the area
stakeholders who routinely operate longer than standard semi -truck loads. During the meetings
alternative options were reviewed. These alternatives were then analyzed by Spack Consulting, a traffic
engineering firm. The traffic analysis is attached for review.
The traffic analysis recommended the option of a T- intersection at Twin Lakes Road and 1715` Avenue.
The T- intersection is proposed to be stop controlled on 1715` Avenue with no control for through traffic
on Twin Lakes Road. This option was also the preferred option as reviewed by the stakeholders. The
stakeholders have been seeking confirmation on the future intersection configurations and access options.
The attached preliminary layout is a representation of the recommendations made in the traffic study.
The study further recommended reducing Twin Lakes Road from four lanes to a 3 -lane concept. A 3-
lane corridor would provide for single through lanes in each direction and designated left and right turn
lanes at all intersections. We will continue to analyze the 3 -lane concept through future geometric design,
but no formal decision is required at this time.
If this item is approved by the Council, the traffic study and memorandum will be added as an addendum
to the 1715` FAST.
Financial Impact
None
Attachments
• Traffic Analysis
• Preliminary Intersection Layout
PV0WIBEO BY
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ALIZEM
TRAFFIC STUDY COMPANY
Technical Memorandum
To: Justin Femrite, P.E., City of Elk River
From: Mike Spack, P.E., P.T.O.E.
Date: January 6, 2014
Re: Traffic Analysis of 171St Avenue & Twin Lakes Road Intersection in Elk River, MN
Purpose of Report and Study Objectives
Changes are proposed for the street and intersection network along 171St Avenue NW near its current
intersection with 170th Lane NW. Based on these changes, a new intersection of 171St Avenue NW /Twin
Lakes Road NW would be created. The purpose of this memorandum is to recommend an intersection
configuration for the new intersection that accommodates traffic patterns expected with the proposed
transportation network.
Summary of Recommendations
Based upon the information and analysis presented in this report, the following minimum configuration
is recommended for the intersection of 171St Avenue NW /Twin Lakes Road:
• One northbound left turn lane and one northbound through lane.
• One southbound through lane and one southbound right turn lane.
• One eastbound left turn lane and one eastbound right turn lane.
• Provide side - street stop sign control at the new intersection of 171St Avenue and Twin Lakes
Road, with the stop signs placed on 171St Avenue and free flowing traffic on Twin Lakes Road to
the new access with Highway 169.
Roadway Network
171St Avenue is an east -west four lane, undivided road with a posted speed limit of 40 mph. A traffic
signal currently controls traffic at its intersection with Highway 169. From that intersection,
171St Avenue provides for travel east through an industrial area with access to several public roads and
private driveways. At the crossing of the BNSF Railroad tracks, the roadway turns to the north and
becomes Twin Lakes Road. Twin Lakes Road is a four lane, divided road that provides access to the
Northstar Commuter Rail station and beyond. Figure 1 in the Appendix shows the existing road
configuration.
As part of the effort to improve safety and mobility on Highway 169, the existing intersection with
171St Avenue is proposed to be closed. A new access, potentially a full interchange in the future, would
be created south of the 167thAvenue intersection. This new road intersecting Highway 169 would be
extended north creating a new north -south corridor that intersects with 171St Avenue and Twin Lakes
Road. As currently planned, the new roadway would be an extension of Twin Lakes Road, providing a
continuous corridor from the new Highway 169 access to the Commuter Rail station and beyond. The
result of these roadway and intersection changes is a major shift of traffic from the current 171St Avenue
corridor to the new Twin Lakes Road corridor.
Spack Consulting 2 of 6 1715` Ave & Twin Lakes Rd Traffic Analysis
Figure 2 in the Appendix shows two layouts developed for this new intersection of 171" Avenue and
Twin Lakes Road. A two lane roundabout was originally proposed as a method to accommodate the
shifting traffic patterns associated with the proposed network changes. After discussions with area
businesses and their primary concern regarding the accommodation of over -sized semi - trucks, a
traditional intersection was also developed as an option for this new intersection.
Traffic Volumes
Shifting the major Highway 169 access from 171" Avenue to 167th Avenue will result in significant travel
pattern changes in this area. Traffic volumes for the future condition are necessary to properly evaluate
the most appropriate intersection configuration. The a.m. and p.m. peak hour volumes were obtained
from the 1715tAvenue Area AUAR completed in 2011. From this report, the traffic volumes forecasted
with the proposed future Highway 169 access with Twin Lakes Road are labeled as Scenario 2.
The Scenario 2 volumes were adjusted through the network to match the proposed roundabout and
traditional layouts. Volumes were then added in for three existing businesses that will have their
driveways altered by these changes. These businesses are:
• LeFebvre Companies, located north of 171" Avenue and west of the railroad tracks,
• Morrell Companies, located south of 171" Avenue and west of the railroad tracks, and
• Preferred Power Coating, located southwest of the proposed new intersection.
Traffic volumes for these sites were determined by using building square footage and rates from the
Institute of Transportation Engineers' Trip Generation Manual, 9t" Edition. Although the traffic from
these sites is likely already included in the traffic volumes for the public intersections, they are necessary
to fully evaluate the proposed roadway changes and also presents a conservatively high estimate of the
traffic in the area. The traffic volumes developed for each scenario can be seen in the Appendix.
Alternative Configurations
For this memorandum, the traffic control and the geometry of the new 171" Avenue and Twin Lakes
Road intersection were reviewed for other potential configurations. Based upon the traffic volumes and
surrounding site, a grade- separated crossing is not appropriate. This includes several alternative
intersection types, such as an echelon interchange or center turn overpass interchange. Given the
roadway is designed to provide access to surrounding businesses, access management options such as a
restricted crossing U -turn intersection, are also not advisable. The relatively low volumes, compared to
the warrant thresholds, also eliminated traffic signal control.
However, a review of the traffic volumes did reveal that a four -lane roadway has a much greater
capacity than the volumes presented in the previous section. Therefore, a three -lane roadway was
considered for Twin Lakes Road, providing one through lane in each direction with a center, two -way
left turn lane. The approach lanes at the study intersection would then be configured as follows:
• One northbound left turn lane and one northbound through lane
• One southbound through lane and one southbound right turn lane
• One eastbound left turn lane and one eastbound right turn lane
Since traffic signal control is not appropriate, stop sign control was considered. For this future
condition, stop control on 171" Avenue is most appropriate with Twin Lakes Road traffic able to proceed
without stopping. This alternative configuration, in addition to the roundabout and four -lane stop
control options, is shown in Figure 3 in the Appendix.
Spack Consulting 3 of 6 1715` Ave & Twin Lakes Rd Traffic Analysis
Alternatives Evaluation
With three alternatives developed, several measures of effectiveness were developed for comparison
purposes. Each measure is described briefly below:
Level of Service — Using the methodology presented in the Highway Capacity Manual, intersections are
assigned a "Level of Service" letter grade for the peak hour of traffic based on the number of lanes at
the intersection, traffic volumes, traffic control, and other characteristics. Level of Service A (LOS A)
represents light traffic flow (free flow conditions) while Level of Service F (LOS F) represents heavy traffic
flow (over capacity conditions). Generally, a LOS D is considered acceptable by most public agencies.
Individual movements are also assigned LOS grades. For this memorandum, the p.m. peak hour was
analyzed since it has the highest overall traffic volumes.
Vehicle Stacking — Along with LOS results, the Highway Capacity Manual methodology can calculate the
number of vehicles that will stack, or queue, while waiting to proceed through an intersection. Shorter
queues are generally consistent with shorter delays and less congestion. As with the Level of Service,
the vehicle stacking measure of effectiveness was based upon the p.m. peak hour with the highest
overall traffic volumes.
Ability to Accommodate Over -sized Trucks — Given the industrial nature of the surrounding area and
conversations that occurred when the roundabout alternative was presented, any alternative must be
able to satisfactorily accommodate over -sized semi - trucks. In this case, accommodation generally refers
to limiting roadway curves, providing wide intersection radii, and the ability to provide wide travel lanes.
Safety — Safety can be measured in many different ways. For the purposes of this memorandum, safety
refers to the potential for vehicle conflicts, and thus crashes, at the intersection or surrounding corridor.
For instance, a four -lane corridor has a greater potential for conflicts due to the potential for sideswipes
on the corridor and more vehicle conflict points at an intersection.
Right -of -Way Needs — Sufficient Right -of -Way has already been reserved for a four -lane section and a
roundabout for the new intersection if that is the chosen configuration. Therefore, this evaluation
refers to the ability to return some Right -of -Way to the surrounding private property owners if not
needed.
Future Flexibility — The Scenario 2 traffic volumes are projections of what may occur in the future based
on many assumptions. A change in one or more assumptions that went into the projections could alter
those traffic volumes. This measure of effectiveness therefore refers to the ability to accommodate
geometric changes if the traffic volumes are different than expected.
Cost — Although detailed cost estimates were not developed for each alternative, the relative cost
between alternatives can be compared for this measure of effectiveness.
Table 1 presents the results of the alternative comparison based upon the measures of effectiveness
discussed above. Each alternative was compared against the others for the purposes of this summary
table and given a ranking of one to five. A ranking of one represents the best option for a particular
measure while a ranking of five represents the worst option. Ties, or the same ranking, were given to
alternatives with relatively similar results.
Spack Consulting 4 of 6 1715` Ave & Twin Lakes Rd Traffic Analysis
Table 1 -171St Avenue and Twin Lakes Road Intersection Evaluation
Roundabout: 1 1 4 4 5 5 5
Four -Lane Corridor
Stop on 171st Ave: 3 3 5 3 4 4 4
Four -Lane Corridor
Stop on 171st Ave: 2 1 1 1 1 1 1
Three -Lane Corridor
'The top line refers to the traffic control at the intersection and the second line refers to the number of lanes provided on
the Twin Lakes Road corridor.
2 Synch ro /SimTraffic analysis using the volumes developed with Scenario 2 traffic.
Summarizing the rankings provides the following results:
Table 2 —171St Avenue and Twin Lakes Road Intersection Evaluation Summary
i ne top line refers to the traffic control at the intersection ana the secona line refers to the numoer of lanes proviaea on
the Twin Lakes Road corridor.
Based on this evaluation, the three -lane corridor is the best configuration for the Twin Lakes Road
corridor with the upcoming changes. For the intersection of 171St Avenue and Twin Lakes Road, side -
street stop control is the best traffic control, with the stop signs on 171St Avenue.
This evaluation is based upon growth assumptions that went into the 171" Avenue Area AUAR. With
high confidence in the future traffic volumes, there is an opportunity to reduce the amount of right -of-
way needed with a three -lane corridor. However, right -of -way could also be preserved in case volumes
grow unexpectedly and require an additional through lane in each direction at some point in the future.
Spack Consulting 5 of 6 1715` Ave & Twin Lakes Rd Traffic Analysis
Other Corridor Observations
While analyzing the intersection of 171" Avenue and Twin Lakes Road in detail, general observations
were also made regarding the roadway network around the study intersection. The following comments
are based upon the existing and expected volumes and traffic operations at other intersections.
As an industrial area, the amount of truck traffic is high, likely close to ten percent of all traffic. For
comparison, heavy trucks are usually about three percent of all traffic. With this truck traffic, including
over -sized trucks, wide travel lanes of 14- to 16 -feet would assist in their movements. Similarly, large
corner radii of 50 -feet or greater would help prevent encroachment into other lanes. As the geometric
design for the area is developed, a larger than standard design vehicle would be appropriate to ensure
truck movements, particularly over -sized trucks, are able to move efficiently.
Although this memorandum studied the 171" Avenue and Twin Lakes Road intersection, the future Twin
Lakes Road intersections to the south are expected to have more traffic. This includes more turning
vehicles and higher overall volumes. A three -lane road for Twin Lakes Road is still expected to
accommodate this traffic, but turn lanes will be necessary, including right turn lanes. These
intersections also have a greater potential for future signalization based upon the expected traffic.
Private driveway accesses on Twin Lakes Road immediately southwest of the railroad tracks are
currently expected to remain under the alternatives developed. Ideally, intersections would not be
located that close to a railroad crossing to minimize the potential vehicle -train conflicts. Limiting the
accesses to right in /right out or relocating the driveways to other public roads should be examined in
the future. If the accesses are limited, examining the new routes for trucks will be important, including
limiting their need for multiple track crossings or the need for u -turn movements.
As noted earlier, Twin Lakes Road is a four -lane divided roadway to the north of the railroad tracks. The
existing daily traffic and projected Scenario 2 daily traffic is within the capacity of a three -lane road with
right turn lanes. Therefore, Twin Lakes Road could be re- striped, reducing the through lanes to one in
each direction. Right turn lanes would also be needed at key intersections, which may require some
construction. The additional pavement could then be used as a shoulder for disabled vehicles and
pedestrian /bicycle movements.
Similarly, the traffic volumes on 171" Avenue to the west of the future Twin Lakes Road intersection are
within the capacity of a three -lane road. Re- striping this corridor is also a possibility as part of the
planned intersection construction.
Spack Consulting 6 of 6 1715` Ave & Twin Lakes Rd Traffic Analysis
Conclusions and Recommendations
Based upon the information and analysis presented in this report, the following is recommended:
• Construct the new Twin Lakes Road corridor that will extend south from the railroad crossing to
a new access with Highway 169 as a three -lane roadway (one through lane in each direction
with a center left turn lane) with right turn lanes provided at major intersections.
• Provide side - street stop control at the new intersection of 171" Avenue and Twin Lakes Road,
with the stop signs placed on 171" Avenue. Traffic on Twin Lakes Road should be able to
proceed without stopping to reach the new access with Highway 169.
• Other intersections on Twin Lakes Road to the south of the 171" Avenue intersection should
also have side - street stop sign control (Twin Lakes Road traffic allowed to proceed without
stopping). However, these intersections are potential candidates for signalization and should be
monitored into the future.
• Due to the high amount of truck traffic, including over -sized trucks, wide lanes and intersection
corner radii should be provided.
• Depending upon the confidence of the future traffic projections and growth assumptions, the
corridor right -of -way could be preserved to allow for future expansion or reduced with some
land returned to surrounding private owners.
• Efforts should be made to relocate or limit the private driveways on Twin Lakes Road near the
railroad crossing, if it can safely be accomplished without significant impacts to the businesses.
• The existing and future 171" Avenue corridor and Twin Lakes Road corridor (north of the
railroad crossing) both have existing and expected future traffic volumes within the capacity of a
three -lane roadway section and could be restriped.
Attachments
A. Figures 1 - 4
• Figure 1: Existing Road Configuration
• Figure 2: Possible Configurations
• Figure 3: Alternative Configurations
• Figure 4: Recommended Configurations
B. Traffic Volumes
C. Synchro /SimTraffic Simulation Results
Appendix A - Figures
S ack Figure 1
Existing Network
P�TFETRAFFIC STUDY COMPANY
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Traffic Analysis Al 171st Ave /Twin Lakes Rd - Elk River
Appendix A - Figures
S ack Figure
Corridor and Intersection Options
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Traffic Analysis A2 171 st Ave /Twin Lakes Rd - Elk River
Sack
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Appendix A - Figures
Figure 3
Alternative Configurations
Configuration 1:
Stop Sign on 171st Ave
Four Lanes on Twin Lakes Rd south of 171st Ave
Configuration 2:
Two Lane Roundabout
Four Lanes on Twin Lakes Rd south of 171st Ave
Configuration 3:
Stop Sign on 171st Ave
Three Lanes on Twin Lakes Rd south of 171st Ave
Traffic Analysis A3 171st Ave /Twin Lakes Rd - Elk River
Spack
TRAFFIC STUDY COMPANY
Appendix A - Figures
Figure 4
Recommended Configuration
Ra 0
t
North
Not to Scale
Recommended Geometry and Control
using Scenario 2 Volumes
Traffic Analysis A4 171st Ave /Twin Lakes Rd - Elk River
Appendix B - Traffic Volumes
Roundabout Layout Traffic Volumes
T
AM Existing Roundabout
i 6 -t 34 <i \ 4 D
ZY
193 � �9
PM Existing Roundabout
w `/ A ^ \J V a�Pio
m1
1 4
}
343
56T Y
yo
47 1 Q
a
t
S
t
AM Scenario 2 Roundabout
1 w
aoa
/\
f4
as
is o
S
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_L
45 T 6
Scenario 2 Round(about
(PM}
/Z
180
Traffic Analysis B 1 171st Ave /Twin Lakes Rd - Elk River
Appendix B - Traffic Volumes
Traditional Layout Traffic Volumes
�) U)(D
AM Existing Traditional
9 ) r 16 / o
,so , S {- 32 38 o
PM Existing Traditional
Traffic Analysis B 2 171st Ave /Twin Lakes Rd - Elk River
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yp
coo
AM Scenario 2 Traditional
`J a `_1
aoo
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7'S'10�
0
PM Scenario 2 Traditional
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0
20
r
40
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Appendix C - Synchro /SimTraffic Simulation Results
171 st Ave & Twin Lakes
Scenario 2 PM Volumes 12/22/2014
Summary of All Intervals
Run Number
1
2
3
4
5
Avg
Start Time
4:59
4:59
4:59
4:59
4:59
4:59
End Time
6:00
6:00
6:00
6:00
6:00
6:00
Total Time (min)
61
61
61
61
61
61
Time Recorded (min)
60
60
60
60
60
60
# of Intervals
2
2
2
2
2
2
# of Recorded Intervals
1
1
1
1
1
1
Vehs Entered
8425
8514
8486
8383
8474
8457
Vehs Exited
8408
8469
8461
8365
8459
8432
Starting Vehs
88
77
85
86
92
85
Ending Vehs
105
122
110
104
107
108
Travel Distance (mi)
1839
1856
1853
1830
1851
1846
Travel Time (hr)
316.6
297.5
305.7
269.6
331.2
304.1
Total Delay (hr)
251.8
232.1
240.3
205.0
265.9
239.0
Total Stops
2211
2280
2343
2271
2231
2268
Fuel Used (gal)
122.7
119.0
120.6
112.1
126.5
120.2
Interval #0 Information Seeding
Start Time 4:59
End Time 5:00
Total Time (min) 1
Volumes adjusted by Growth Factors.
No data recorded this interval.
Interval #1 Information Recordi
Start Time 5:00
End Time 6:00
Total Time (min) 60
Volumes adjusted by Growth Factors.
Run Number
1
2
3
4
5
Avg
Vehs Entered
8425
8514
8486
8383
8474
8457
Vehs Exited
8408
8469
8461
8365
8459
8432
Starting Vehs
88
77
85
86
92
85
Ending Vehs
105
122
110
104
107
108
Travel Distance (mi)
1839
1856
1853
1830
1851
1846
Travel Time (hr)
316.6
297.5
305.7
269.6
331.2
304.1
Total Delay (hr)
251.8
232.1
240.3
205.0
265.9
239.0
Total Stops
2211
2280
2343
2271
2231
2268
Fuel Used (gal)
122.7
119.0
120.6
112.1
126.5
120.2
Elk River
Spack Consulting
SimTraffic Report
Page 1
Traffic Analysis C1 171st Ave /Twin Lakes Rd - Elk River
Appendix C - Synchro /SimTraffic Simulation Results
171 st Ave & Twin Lakes
Scenario 2 PM Volumes
12/22/2014
1: Stop on 171 st & Four Lane Rd Performance by movement
Movement SEL SER NEL NET SWT SWR
All
Denied Del /Veh (s) 0.1 0.1 2.5 0.2 0.1 0.2
Total DelNeh (s) 31.7 2.9 5.8 0.4 0.4 0.4
6: Roundabout & Four Lane Rd Performance by movement
0.3
1.0
Movement NBL NBR SEL SER SWU SWL SWR All
Denied DelNeh (s) 0.5 0.2 0.1 0.1 0.4 0.4 0.1 0.3
Total DelNeh (s) 6.8 5.1 5.8 4.0 7.3 7.5 5.0 5.9
12: Stop on 171 st & Three Lane Rd Performance by movement
Movement EBL EBR NBL NBT SBT SBR
All
Denied Del /Veh (s) 0.1 0.1 3.3 1.8 0.3 0.2
Total Del /Veh (s) 41.7 5.3 5.8 1.1 0.6 0.4
1.3
1.7
Total Network Performance
Denied Del /Veh (s)
Total DelNeh (s)
Elk River
Spack Consulting
Traffic Analysis
79.7
18.0
SimTraffic Report
Page 2
C2 171 st Ave /Twin Lakes Rd - Elk River
Appendix C - Synchro /SimTraffic Simulation Results
171 st Ave & Twin Lakes
Scenario 2 PM Volumes 12/22/2014
Intersection: 1: Stop on 171st & Four Lane Rd
Movement
SE
SE
NE
SW
SW
Directions Served
L
R
L
T
TR
Maximum Queue (ft)
54
54
86
4
18
Average Queue (ft)
17
20
32
0
1
95th Queue (ft)
46
47
68
3
10
Link Distance (ft)
698
698
570
616
616
Upstream Blk Time ( %)
250
Storage Blk Time ( %)
Queuing Penalty (veh)
Queuing Penalty (veh)
Storage Bay Dist (ft)
250
Storage Blk Time ( %)
Queuing Penalty (veh)
Intersection: 6: Roundabout
& Four Lane Rd
Movement
NB
NB
SE
SW
SW
Directions Served
LR
R
LR
ULR
R
Maximum Queue (ft)
174
158
64
279
99
Average Queue (ft)
60
20
17
79
3
95th Queue (ft)
142
86
50
178
42
Link Distance (ft)
497
497
570
492
492
Upstream Blk Time ( %)
250
Storage Blk Time ( %)
Queuing Penalty (veh)
Queuing Penalty (veh)
Storage Bay Dist (ft)
Storage Blk Time ( %)
Queuing Penalty (veh)
Intersection: 12: StoD on 171st & Three
Lane Rd
Movement EB EB NB SB SB
Directions Served
L
R
L
T R
Maximum Queue (ft)
62
56
78
4 17
Average Queue (ft)
16
16
34
0 1
95th Queue (ft)
46
43
69
3 7
Link Distance (ft)
415
415
465 465
Upstream Blk Time ( %)
Queuing Penalty (veh)
Storage Bay Dist (ft)
250
Storage Blk Time ( %)
Queuing Penalty (veh)
Elk River
Spack Consulting
SimTraffic Report
Page 3
Traffic Analysis C3 171 st Ave /Twin Lakes Rd - Elk River
City of
Elk
River
171ST AVENUE - TWIN LAKES ROAD
PRELIMINARY DESIGN
JANUARY 20, 2015
Scale: 1 INCH = 400 FEET