HomeMy WebLinkAbout7.1 2nd LftTrnLnEbndDB@VPCITY OF DUBLIN
AGENDA STATEMENT
City Council Meeting Date: December 14, 1987
SUBJECT:
Second Left Turn Lane, Eastbound Dublin Blvd. at
Village Parkway
EXHIBITS ATTACHED:
1) Report from TJKM
2) Diagram of Proposed Change (2 pages)
RECOMMENDATION: /~z ~-~~/"~pr°ve 80 feet of striping for westbound right-turn
/~'O?'lane onto northbound Village Parkway, and direct Staff
to proceed with one of the following options:
(a) include the full scope of work within the 1988-89
proposed CIP, or (b) begin the design process at this
time and include the construction cost in the 1988-89
proposed CIP, which will require a budget transfer in
the amount of $5,000.
FINANCIAL STATEMENT:
Estimated cost of 80 feet of striping to be done as
soon as possible is $200. Estimated cost of
improvements is $10,000 to $15,000; estimated cost of
design and administration is $3,000 to $5,000.
DESCRIPTION:
At a recent meeting, the City Council requested that Staff investigate
the feasibility of creating a second left turn lane for eastbound Dublin
Boulevard at Village Parkway. This second left turn lane is consistent with
the ultimate planned improvements for Dublin Boulevard.
TJKM, the City's Traffic Engineer, has studied the proposed improvement
on the basis of existing conditions and finds as follows:
Service Level
The intersection level of service would be improved significantly by
this proposed modification (from Level D to Level C during the noon hour and
from Level D to Level B during the late afternoon peak hour). The overall
cycle length would be significantly shortened, which would improve the
perceived signal operation for vehicles in other movements, and the lengths of
the queues at other approaches would be reduced.
Required Modifications
New detectors would need to be installed for the eastbound through lane,
and the existing detectors in the inner through lane would need to be modified
to function as left-turn detectors. The signal would be modified
simultaneously with the restriping. Existing signal indications are not
adequate; the existing head would have to be modified or replaced. The
specific requirements would be determined as part of the signal modification
plan.
Two eastbound left turn lanes and two through lanes will fit within the
existing curb-to-median width. On-street parking is already prohibited on the
south side of Dublin Blvd. between Village Parkway and the Zone 7 channel. In
order to allow for transitioning, parking should also be prohibited for an
additional 420 feet to the west (in other words, under 1-680 and in front of
the Dublin Cinema). This parking consists of approximately 10 spaces, only
four of which are in front of the theater, and is very rarely utilized. Its
elimination should not inconvenience any of the businesses in the area.
Notices regarding the proposed improvements have been sent to businesses and
property owners at or near the intersection.
A resolution establishing the no parking zone must be adopted in order
to implement this recommendation and will be placed on a future agenda if and
when the improvements are made.
Westbound Right Turn Lane
TJKM's report discusses the possible conflict involving traffic turning
right from westbound Dublin Blvd. onto northbound Village Parkway. At this
time, TJKM recommends retaining the existing YIELD sign rather than installing
a STOP sign or removing the triangular island. It is recommended, however,
that the westbound right turn lane be striped an additional 80 feet further
east in order to more ~clearly delineate where a vehicle turning right must
make the commitment to turn right. This curb is already designated a no-
parking zone. Staff would recommend performing this particular striping as
soon as possible in order to alleviate conflicts between vehicles which pass
on the right to make the turn onto Village Parkway and those in the through
lane which decide to turn right at the last minute.
Cost Factor and Recommendation
TJKM estimates that construction cost of these improvements would range
between $10,000 and $15,000, including signal modification, detector
modification, and striping. A more definite figure would be determined during
the design process. An additional $3,000 to $5,000 will be needed to prepare
design drawings and specifications and for project administration and
inspection. Because of the significant Service Level improvement at this
intersection, Staff recommends that the City Council authorize the 80 feet of
striping for the westbound right turn lane and direct Staff to proceed with
one of the following options: (a) to include the total project in the
proposed 1988-89 Capital Improvement Program (design as well as construction)~
or (b) to proceed with the design phase of the project at this time and
include the construction phase cost in the proposed 1988-89 CIP. If option
(b) is selected, a budget transfer in the amount of $5,000 would be necessary.
Staff estimates the design process will require approximately two to
three months to complete, and it is anticipated that Staff would request
approval from the City Council to solicit bids on this project during the
current Fiscal Year, with construction to take place in July of 1988 so that
construction costs would fall into the 1988-89 Fiscal Year.
MEMORANDUM
4637 Chabot Drive, Suite 214
Pleasanton Ca. 94566
(415) 463-0611
DATE:
TO:
FROM:
SUBJECT:
November 16, 1987
Lee Thompson
Michelle DeRobertis
Eastbound double left turns on Dublin Boulevard at Village Parkway
At your request, we have investigated the feasibility of striping two eastbound
left-turn lanes on Dublin Boulevard at Village Parkway. We compared the request
with the Dublin Boulevard Plan line. Since double eastbound left-turn lanes are
shown on the Dublin Boulevard Plan Line, this request is consistent with ultimate
planned improvements for Dublin Boulevard. We reviewed the implications of
providing double left-turn lanes in the short term on the signal operation, the
resulting lane widths, the on-street parking, and on other conflicting movements at
the intersection.
Traffic Signal Operation
Vehicle turning templates were used to assess the ability of the intersection to
accommodate eastbound double left-turn lanes simultaneously with the westbound
left turn movement, i.e. in the same signal phase. It was determined that the
eastbound double left-turning vehicles would not conflict with the westbound left-
turning vehicles. Therefore, the existing left-turn phasing which allows the
eastbound and the westbound left-turn movements to proceed simultaneously could
be retained, and split phase operation would not be necessary.
Providing double eastbound left-turn lanes would necessitate installing new
detectors for the eastbound through movement and relocating the existing detectors
in the two through lanes to fit within the new lane lines. The existing detectors in
the inner (northernmost) through lane will also have to be rewired to function as
left-turn detectors. Such changes would require a signal modification plan and
~vould be required simultaneously with the re-striping of the eastbound lanes to
have two through and two left-turn lanes.
The signal indications for the eastbound left turn movement would not be
adequate for the re-striped lanes. A new left-turn signal indication, either by
reprogramming the existing signal head or by replacing the signal head, would be
necessary. The specific requirements would be determined as part of the signal
modification plan.
Two eastbound left turn lanes would improve the existing intersection level of
service during both the noon hour and the late afternoon peak hour by at least one
service level, (from LOS D to LOS C during the noon hour and from LOS D to
LOS B during the late afternoon peak hour). Because the signal is traffic-actuated,
with a maximum timing of 55 seconds for the eastbound left-turn phase alone, the
overall cycle length would be significantly shortened with two eastbound left turn
lanes. This would improve the perceived signal operation for vehicles in other
movements, and would also reduce the length of the queues at the at~proaches of
the other movements.
PLEASANTON-SACRAMENTO.FRESNO.CON£ORD
Mr. Lee Thompson -2- November 16, 1987
Lane Re-striping and On-street Parking
Two eastbound double left-turn lanes could fit within the existing curb to median
width of 46 feet. The two left-turn lanes should be 10 feet wide, the northernmost
through lane should be 11 feet wide and the curbside through lane should be
15 feet wide. On-street parking on Dublin Boulevard is currently prohibited (via
red curb) on the south side of the intersection from Village Parkway west to the
drainage channel. In order to have adequate transitioning, parking should be
prohibited via red curb for an additional 420 feet to the west, (i.e. underneath
1-680).
At approximately 740 feet west of Village Parkway, the striping should deviate
from the existing striping in order to shift the through lanes to the south to fit two
left-turn lanes. The recommended transition and lane striping is depicted in
Figure 1.
Impacts on Westbound Right-Turn movement.
The westbound to northbound right turn movement is controlled by a YIELD sign
due to the raised island which separates the right-turn movement from the other
westbound movements. Although the right-turners are supposed to yield to all
other traffic, including the eastbound to northbound left-turners, there is such a
high demand for the right-turn movement that the right-turners try to squeeze
through during all phases. The major movements that conflict with the westbound
right-turners are the eastbound left-turners and the southbound U-turners. The
situation is complicated by the fact that many left turners turn into the curbside
lane to enter the driveways near the intersection. Many right-turners, however,
assume that the curbside lane is available for their turn. Conflicts and near misses
occur in front of the shared Wendy's/Kentucky Fried Chicken driveway.
The Dublin Boulevard Plan Line indicates that, ultimately, this island will be
removed and that right-turners will be brought under signal control. This will
require relocating the existing signal pole on the island and other signal
modifications. Although the intersection operation would be improved if the right-
turners were brought under signal control, removing the island and relocating the
signal pole would involve considerable expense. The benefits of both retaining the
YIELD sign and replacing it with a STOP sign were considered. If the YIELD
sign were retained, the proportion of signal time that is allotted to the eastbound
left turners would be significantly reduced, thereby reducing the right-turning
vehicles' impatience. Also, having two lanes o£ eastbound left-turners should cause
the right-turners to obey the YIELD control more effectively, since they would
observe left-turning vehicles turn into the curbside lane. We feel that replacing
the YIELD sign with a STOP sign would reduce some confusion and would
eliminate potential conflicts between the westbound right-turners and the
eastbound left-turners. However, it was felt that the potential for the right-turners
to "back-up" and to block the westbound through movement during their green
phase was too great. Therefore, it is recommended that the island and the YIELD
sign be retained in the interim before the ultimate improvements are implemented.
Although we feel the overall intersection operation will improve due to the double
eastbound left-turn lanes, this intersection should be monitored, and the
recommendation re-evaluated after the double left-turn lanes are implemented. It
may be necessary to replace the YIELD sign with a STOP sign or even to remove
the island if the number of conflicts increase, and the intersection operation
deteriorates.
Mr. Lee Thompson -3- November 16, 1987
It is also recommended that the lane for westbound right-turners be striped an
additional 80 feet further to the east, to approximately as far east as the existing
westbound left-turn lane. This would reduce the conflicts between westbound
vehicles by more clearly delineating where a vehicle desiring to turn right must
make the commitment to turn right. This striping change is shown in Sheets 1
and 2. Since the curb along this section of Dublin Boulevard is already painted
red, no additional parking restrictions would be necessary.
Conclusion
Two eastbound left turn lanes can be accommodated with the existing signal
phasing and in the existing curb-to-median width at the eastbound approach of
Dublin Boulevard at Village Parkway. However, a signal modification plan would
be necessary in order to design the required changes to the detectors and to
determine the correct signal indication modifications for the eastbound left-turn
movement. The signal modification plan would cost approximately $3,000 to
$4,000. The cost of the relocating existing detectors, installing new detectors,
related rewiring and controller changes would cost approximately $5,000.
Depending on the extent of the necessary changes, the new signal indication would
cost between $1,000 and $5,000. The cost of re-striping the eastbound lanes would
be approximately $I,000. Therefore, the total cost of implementing double
left-turn lanes would range from $10,000 to $15,000.
The overall intersection operation would improve by providing double left-turn
lanes. The cycle length would be reduced, resulting in less delay and shorter
queues at the other movements. The level of service would improve from LOS D
to LOS C, and LOS B, during the midday and late afternoon peak hours,
respectively.
The Dublin Boulevard Plan Line depicts that, ultimately, the westbound right turn
movement will be brought under signal control by removing the raised island.
Although this would benefit the existing situation as well as the conditions after
double left-turn lanes are implemented, it is not required. Having two lanes of
eastbound left-turners should cause the westbound right-turners to be more aware
of the potential for conflicts and to obey the YIELD sign more effectively.
Therefore, it is recommended that the existing YIELD sign be retained and the
intersection be monitored. If the conflicts continue or worsen, further
improvements should be implemented. In addition, it is recommended that the
westbound right-turn lane be striped for an additional 80 feet to the east. This
would make westbound drivers more conscious of the potential for conflicts
between vehicles which have committed themselves to turning right and other
westbound vehicles in the curbside lane.
nlc
Attachments
157-001
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