HomeMy WebLinkAbout2012-10-03 PACKET 09.A.REQUEST OF CITY COUNCIL ACTION COUNCIL AGENDA
MEETING ITEM #
DATE 10/3/2012
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PREPARED BY Public Works Les Burshten
ORIGINATING DEPARTMENT STAFF AUTHOR
COUNCIL ACTION REQUEST
Receive response to previously raised Council comments and requests regarding overview of
Traffic Control Changes 2012.
SUPPORTING DOCUMENTS:
❑ MEMO /LETTER:
❑ RESOLUTION:
❑ ORDINANCE:
❑ ENGINEERING RECOMMENDATION:
❑ LEGAL RECOMMENDATION:
® OTHER: Cottage Grove Traffic Control Changes — 2012, Roger Plum, SEH
ADMINISTRATORS COMMENTS r
City Adrfiinistrator � Date
COUNCIL ACTION TAKEN: ❑ APPROVED ❑ DENIED ❑ OTHER
C: \Documents and Settings \nbelscamper \Local Settings \Temporary Internet Files\ Content .Outlook \OFUXMGAF \Council Action Form Cottage
Grove Traffic Changes overview.doc
COTTAGE GROVE TRAFFIC CONTROL CHANGES - 2012
90` Street & Jamaica Avenue
On July 11, 2012, the left turn control was changed on Jamaica Avenue from protected -only (left turns
allowed only on green left arrow) to protected - permissive (left turns allowed either on a green left
arrow, or on a flashing yellow arrow while yielding to oncoming traffic). The flashing yellow arrow is
displayed during the time that the through traffic in the opposite direction has a green light.
Jamaica Avenue & E Point Douglas Road
On July 11, 2012, the left turn control was changed on Jamaica Avenue from protected -only (left turns
allowed only on green left arrow) to protected - permissive (left turns allowed either on a green left
arrow, or on a flashing yellow arrow while yielding to oncoming traffic). The flashing yellow arrow is
displayed during the time that the through traffic in the opposite direction has a green light.
For both of these intersections, the primary goal of the change was to improve efficiency of the
operation, in particular reducing delays for traffic turning left off of Jamaica Avenue. Under the previous
operation, all left- turning traffic on Jamaica was permitted to turn only during the green left arrow.
After transitioning through a short yellow left arrow to a red left arrow, left- turning vehicles had to wait
for all through traffic on Jamaica to finish being served, followed by service to the cross streets — both
directions simultaneously at 90 Street, each direction independently at East Point Douglas — before
being served again. Especially during the peak hours when traffic on Jamaica is heavy in one direction
and light in the other, the left turns had to wait even though there was little or no oncoming traffic.
With the new operation, left- turning traffic still has an interval during which a green left arrow is
displayed and opposing through traffic has a red light, but left turns are also permitted after the green
left arrow has been extinguished, oncoming through traffic receives a green ball (circular indication),
and a flashing yellow left arrow is displayed to left- turning traffic. Turning during the flashing yellow
arrow does require the vehicle driver to judge whether the gaps in oncoming traffic are sufficient to turn
through.
80 Street & Hardwood Avenue /E Point Douglas Road
On August 8, 2012, the geometry on East Point Douglas Road approaching 80` Street from the south
was changed from one left- turn -only lane plus one left- through option lane plus one through -right
option lane to one left- turn -only lane, one through -only lane, and one right- turn -only lane. The
geometry on Hardwood Avenue, approaching 80` Street from the north, was changed from one left -
turn -only lane plus one left- through option lane plus one through -only lane plus one right- turn -only lane
to one left- turn -only lane plus two through -only lanes plus one right- turn -only lane. Pavement "cat -
tracking" was also added through the intersection to help guide southbound motorists traveling across
8 0` Street. These changes are shown in Figures 1 and 2, respectively.
Figure 1. East Point Douglas Road Northbound at 80 Street, beginning August 8, 2012
Figure 2. Hardwood Avenue Southbound at 80 Street, beginning August 8, 2012
In addition, the traffic signal operation for northbound and southbound was also changed, from split
phasing (all northbound traffic served first, followed by all southbound traffic) to protected - permissive
phasing, which allows both northbound and southbound traffic to move simultaneously, with left turns
in both directions permitted to turn either on a left arrow or on a green ball while yielding to oncoming
traffic.
The goals of these changes were:
• To make the intersection operationally more efficient.
o By moving all northbound through vehicles to the center lane, right turning vehicles will
not be blocked by through vehicles and can therefore make right turns on red. In
addition, by converting the signal operation more total time becomes available to
accommodate all northbound and southbound traffic.
o By moving all southbound left- turning vehicles into a single lane, traffic is better
balanced across all four lanes. Less than 20 percent of the southbound traffic on
Hardwood Avenue turns left at 80` Street.
• Improve safety as vehicles depart the intersection.
o Because Hardwood Avenue is curving as it approaches 80` Street, southbound through
vehicles had difficulty in staying in the appropriate lane as they crossed over 80` Street.
The "cat tracking ", painted between the two through lanes, helps motorists maintain
proper lane positioning on the far side of the intersections.
o For those motorists northbound making a left turn toward US Highway 61 prior to the
change, the majority of vehicles turning left from northbound East Point Douglas Road
onto 80` Street throughout the day also turn right onto the entrance ramp to
northbound Highway 61. Under the previous operation, when left turns were permitted
from two lanes, vehicles on the inside (leftmost) left -turn lane which were destined to
Highway 61 had to merge quickly, after completing their left turn, with vehicles from the
center lane who had also turned left and may — or may not — also have been destined to
Highway 61. Knowing this, many drivers destined to Highway 61 would make the left
turn from the center lane, leading to the left lane been very under - utilized. In addition,
some drivers using the leftmost lane would "swing wide" while making their left turn,
essentially "cutting off" drivers turning left from the center lane. Consolidating all left
turns into a single lane eliminates this merging issue on 80` Street between E Point
Douglas Dr and Highway 61.
Observations Since the Changes
At the Jamaica Avenue intersections at 90 Street and at East Point Douglas Road, motorists appear to
have adjusted well to the implementation of the flashing yellow operation in conjunction with the
conversion from protected -only operation to protected - permissive operation. Initially there appeared
to be some hesitation in making left turns during the flashing yellow arrow operation, but that confusion
seems to no longer exist. At Jamaica & 90 there has been only one crash this year, occurring on May
28, before the changes were made. At Jamaica & East Point Douglas, there have been four crashes since
the implementation of the flashing yellow arrow operation. The primary contributing cause for two of
these crashes (July 11 and August 19) was "failure to yield" by traffic turning left from Jamaica onto East
Point Douglas. One crash occurred in the northbound direction; the other crash occurred in the
southbound direction. These crashes were due to driverjudgment error in making a left turn during the
flashing yellow arrow. The othertwo crashes since the flashing yellow arrow installation (September 11
and September 18) were rear -end collisions attributable to inattentive driving.
At the intersection of 80 Street & East Point Douglas Drive /Hardwood Avenue, which was believed to
have the most potentially controversial changes, periodic observations have been made since the
August 8 th conversion. For the southbound direction, there have been no issues with all left- turning
vehicles utilizing only the left -most lane as they approach the intersection. Southbound through traffic
also tends to maintain proper positioning as they cross 80 Street.
On the other hand, northbound left- turning motorists (from East Point Douglas Drive onto 80 Street)
initially were relatively slow to recognize the geometric change requiring them to use onlythe leftmost
lane, in spite of signing and flagging both in advance of and at the intersection. One week afterthe
signing and pavement marking changes, 20 percent of the left- turning drivers were continuing to use the
center lane. In response to this lack of attention to — or defiance of —the changes, on August 23, 2012
the City installed barrel- mounted signs on the lane line between the through lane and the right -turn
lane, as shown in Figure 3.
Figure 3. Enhanced Notification of Changes, Northbound East Point Douglas Road at 80 Street.
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In less than a week, when observations were next conducted, lane compliance forthe left turns had
improved to 98 percent, with only a handful of vehicles still turning left from the center lane. As of
September 12, compliance during the weekday afternoon peak period — approximately 4:30 to 6:30 PM
— remained at 98 percent, with virtually 100 percent compliance during the remainder of the day and on
weekends.
During the last week of September, the barrel- mounted signs located on the lane lines were removed.
These signs had been very effective in conveying the new desired lane use to motorists, especially to
those northbound motorists turning left onto 80 Street. On October 1, the afternoon peak period was
observed for over one hour to determine if compliance would degrade after the signs were removed.
Fortunately, compliance without the barrels in place remains at 98 percent during that time period.
One concern raised relative to forcing all northbound left- turning traffic into a single lane was the
potential for a queue extending from 80` Street back to the former Home Depot driveway exit and
potentially to the previous signalized intersection (East Point Douglas Road & Grove Plaza). Based on
field observations, the left -turn lane can hold approximately eight vehicles, as shown in Figure 4.
Following the intersection changes, the maximum queue was observed to exceed eight vehicles in three
cycles of the 56 cycles observed during the morning peak period and in 10 of the 70 cycles observed
during the afternoon peak period. The longest queue observed during these time periods — occurring
only once — was 18 vehicles. The queue did extend back to the Grove Plaza signalized intersection on
two occasions. However, in all cases where a vehicle exiting the former Home Depot driveway (shown
on the right side in Figure 4) was initially prevented from entering the northbound left turn lane by a
queue, that vehicle was able to enter the left turn lane while the signal indication for northbound traffic
was still green.
Vehicle crash history at this intersection in 2012 revealed that there have been a total of seven crashes.
Of those only one has occurred (on August 31) since the signal, signing and pavement marking changes
were made on August 8 From the crash report, it is not clear whether that one crash could have been
attributed to the changes made, as the accounts of the drivers involved and witnesses are inconsistent.
Construction barricades unrelated to the August 8 operational changes were noted on the crash report,
and could have contributed to confusion.
Figure 4. Northbound Left Turn Queue on East Point Douglas Drive at 80 Street