A-3. Discuss 86th Street and Highway 101 Intersection Operations in Conjunction with the Mission Hills Senior Living development 1 T Y
CITY OF CIIANIIASSEN
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S Chanhassen isa Community for Life-Providing for Today and Planning for Tomorrow
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MEMORANDUM
TO: Todd Gerhardt, City Manager ff''
FROM: Paul Oehme, Director of Public Works/City Engineer d'U
DATE: May 22, 2017
SUBJ: Discuss W. 86th Street and Highway 101 Intersection Operations in Conjunction
with the Mission Hills Senior Living Development
BACKGROUND
At the May 8, 2017 Council meeting for the Mission Hills Senior Living Development item, staff
was directed to bring back the Highway 101 and W. 86th Street intersection at a future Council
meeting for further discussion.
DISCUSSION
The developer for the Senior Living Development was directed to complete a traffic study to
determine what impacts the proposed development would create compared with existing
conditions. SRF Consultants completed the traffic study in July 2016. The main objectives of
the study was to review the site plan with regard to trip generation, access, circulation, and look
at potential traffic issues with Highway 101 and W. 86th Street intersection operations.
An existing intersection capacity analysis was completed to establish a baseline condition to
which future traffic operations could be compared. The study intersections were analyzed using
Synchro/SimTraffic software (V9.1).
Capacity analysis results identify a Level of Service (LOS), which indicates how well an
intersection is operating. Intersections are ranked from LOS A through LOS F. The LOS results
are based on average delay per vehicle, which correspond to the delay threshold values shown in
the table below. LOS A indicates the best traffic operation while LOS F indicates an intersection
where demand exceeds capacity. Overall, intersection LOS A though LOS D is generally
considered acceptable in the Twin Cities metropolitan area.
Level of Service Criteria for Signalized and Unsignalized Intersections
LOS Signalized Intersection Average Unsignalized Intersection
Designation Delay/Vehicle(seconds) Average Delay/Vehicle (seconds)
A < 10 < 10
B > 10 - 20 > 10 - 15
C > 20 - 35 > 15 - 25
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7700 MARKET BOULEVARD • PO BOX 147 • CHANHASSEN • MINNESOTA 55317
May 22,2017
W. 86th Street&Highway 101 Intersection
Page 2
D > 35 - 55 >25 - 35
E > 55 - 80 > 35 - 50
F > 80 > 50
The following table shows the documented existing intersection side street capacity analysis for
Highway 101 and W. 86th Street and the modeled capacity analysis:
A.M. Peak Hour P.M. Peak Hour
LOS Delay LOS Delay
Existing conditions Highway 101/W. 86th Street B 13 B 10
(1)
With Development Highway 101/W. 86th Street B/C 16 B 14
(1)
(1) The delay shown represents the worst side-street approach delay.
Turning movement counts were obtained for the traffic study and future turning movement
projections were estimated.
A.M. Peak Hour P.M. Peak Hour
Left Right Left Right
Existing conditions Highway 101/W. 86th Street 35 28 13 15
With Development Highway 101/W. 86th Street 68 54 46 43
Crash records data was obtained for the intersection of Highway 101 and W. 86th Street from the
Minnesota Department of Transportation and Carver County. There was one documented
accident in 2015 at this intersection in the past 10 years.
The results of the study show that the intersections of CSAH 101 and Lake Susan Drive, CSAH
101 and W. 86th Street, and W. 86th Street and Mission Hills Drive would have a negligible
change in Level of Service and all the studied intersections are expected to function at acceptable
levels.
Both the traffic study and Carver County cited the intersection of CSAH 101 and W. 86th Street
may need future improvements. City staff will continue to work with Carver County to
determine if improvements at the intersection are recommended from a traffic engineering
standards perspective.
If improvements to the intersection are requested grant funding would most likely not be
available because of the low crash rate.
Staff has reviewed several improvement options that may improve traffic movements during
certain times of the day. Intersection improvements which have been considered include:
installation of signals, construction of a roundabout, and installation of a median acceleration
lane. Signal warrants are not met for this intersection mainly because of low side street traffic
volumes and short delays. If signal warrants were met, the installation of the signal is estimated
to cost $300,000. The estimate to construct a roundabout at this intersection is $500,000.
May 22,2017
W. 861 Street&Highway 101 Intersection
Page 3
Median Acceleration Lanes (MALs) are just what they sound like—an acceleration lane on the
inside median. MALs are intended to allow left turning vehicles from the side streets, or
U-turning vehicles on the mainline,to complete their turn without needing to wait for a gap in
the highway through traffic. In Minnesota at least, MALs are more commonly used for heavy
truck traffic entering a separated highway with a predominate left turn movement. The left lane
is used to accelerate up to speed before merging. MnDOT has constructed MALs on highways
at high fatal/severe crash locations. Theoretically, safety at the intersection is improved by
reducing potential conflicts. Not many MALs are constructed in the state and especially in the
metro area so drivers would have to get use to driving in them. A recent study completed by
MnDOT evaluated how effective MALs are for improving safety. This study found that MALs
have been shown to decrease fatal/high severe injury type crosses compared to intersections
without the MALs. However, overall total crashes were still relatively high with MALs. To
construct a MAL on Highway 101,it is estimated to cost$135,000. At this time, it is unlikely
Carver County would partner with the City to construct a MAL because the intersection has not
been documented to be a safety problem.
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Median Acceleration Lane
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g:\eng\projects\k-o\mission hills 3rd addition\052217 10186thtraffic update.docx