October 12, 2012
Casey Arborway Traffic Comments and Responses
The following comments were submitted by Casey Arborway Design Arborway Group
members and the responses were prepared by MassDOT and the Casey Arborway Design team.
Each comment has been categorized and is repeated below, followed by the response in italics.
Traffic Count Questions and Requests
Comment: MassDOT Traffic and Safety Guidelines call for traffic counts to be done on the
major North/South roads intersecting the Casey Arborway. These were not done. Why not?
Response: Overview of the data collection process and existing traffic volumes for this project were
presented at a Working Advisory Group (WAG) meeting on May 4, 2011. The locations of the traffic
counts were selected by the Project Team in collaboration with MassDOT and the City of Boston based on
previous studies in this area. The locations were determined to allow for a thorough assessment of
potential project impacts. Automatic traffic recordings (ATR) were collected on Casey Overpass and
New Washington Street. Turning movement counts were collected at seventeen intersections. The
turning movement counts collected consisted of 11-hour continuous counts, well in excess of the
MassDOT requirement for four hours of peak period counts. These additional turning movement counts
are more detailed than ATR data and they cover all peak periods throughout the day (7AM-6PM). With
this more in depth count data, the additional ATR’s were not necessary for any of the analysis or
evaluation for this project.
Comment: In June 2012 access to all traffic count data was requested. At least one traffic count
was has been withheld since that time. Please post all traffic count data immediately.
Response: Extensive traffic count data has been made available over the course of this project. It is
unclear which specific counts are referred to in this comment. Appendices B and C of the Functional
Design Report includes the raw traffic count data collected for this project and recent data from the City
of Boston is poste don the project website.
Comment: Where did data for the North/South roads come from? How was it combined with
East/West data taken at different times of the year?
Response: As stated above, eleven-hour turning movement counts were collected at all study area
intersections, which allow us to easily identify the peak periods on the North/South roadways in absence
of ATR data. In addition, historical data is available from previous studies for the North/South roadways.
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All count data for the original 17 study area intersections was collected in June 2010 and the ATR counts
were completed concurrently with the turning movement counts. An additional ATR was collected on the
Casey Overpass in December 2011 but this was not used in the analysis because the volumes were lower
than the original ATR collected. The only additional turning movement count data collected for this
project was for the intersection of Cemetery Road and Morton Street in September 2011.
Comment: No seasonal traffic volume changes were accounted for. Why not?
Response: The seasonal factors were reviewed. However, since June and September represent above
average traffic conditions, traffic volumes were not adjusted as the seasonal factor would have decreased
the volumes incorporated in the study as its intent is to present an average condition. Retaining the
originally counted volumes presents a slightly conservative scenario.
Comment: East/West traffic counts show up to 28,000 vehicles per day. We have been told the
traffic modeling used data from days when the traffic counts were 24,000. Please explain.
Response: The 24,000 vehicles per day is the average daily traffic (ADT) over the 7-day period when the
ATR’s were conducted. ADT is the average traffic volume over a 24-hour period at a given location
during a specific count period; typically 7 days. Although, 28,000 vehicles were observed on specific
weekdays, the ADT is typically referenced for daily volumes. All analysis completed to date is based on
the peak period turning movement counts and not the daily volumes. As such, the ATR data for the midweek peak hours was reviewed to confirm the accuracy of the turning movement volumes.
Large Vehicle Movement Questions
Comment: What are the exact routes the deadhead buses will take to and from the Upper and
Lower Busways?
Response: The deadhead busses from Arborway Yard currently exit onto Washington Street. From
there they will travel southbound directly to the lower busway on Hyde Park Avenue, or continue south
and turn right onto Ukraine Way and then northbound on Washington Street to reach the Upper
Busway. To return to Arborway Yard, the deadhead busses would travel these routes in reverse. A
limited number of deadhead buses access Forest Hills Station from other yards to the east and those buses
would be expected to use the dedicated bus left turn lane to turn onto Hyde Park Avenue.
Comment: The numbers of heavy vehicles in the turn counts seems low? Please explain.
Response: The truck percentages exhibited in the TMCs collected for this project are consistent with the
BTD count data from February 2012, falling within normal daily variations, particularly for the
intersections along the Arborway. The truck percentages from the traffic counts were compared to the
actual MBTA bus data, and upward adjustments were made to the truck percentages at Ukraine Way in
our analysis to reflect the bus data. Note that pick-up and panel trucks are not included in the truck
volume. Using standard traffic engineering practice, a truck is typically considered as a vehicle that has
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six or more wheels.
Comment: At the West Bow Tie U-turning vehicles pass within the space of the sidewalk
crossing. Is a pedestrian signal needed?
Response: See attached graphic. There are three separate zones depicted in the attached drawing. The
green zone is the connection from the on street bike lane to the off street bikepath. Note that the bike
traffic is stopped while U-turns are moving. The blue area is a “Truck Apron” which is a slightly raised
concrete pavement with a mountable curb. The yellow area behind that is sidewalk, separated by a 6”
curb from the truck apron. The movement is designed for a WB-40 truck (a large sized city truck) and a
city/school bus to complete the movement.
Comment: Can transit buses negotiate the right hand turn from westbound Ukraine Way to
northbound Washington St.? If not, what routes do they take? What is the largest vehicle
accommodated here?
Response: Both City/School Buses and WB-40 Trucks are accommodated in this turning movement.
Comment: How will trucks/buses that can’t negotiate the East and West Bow Ties be handled?
What is the largest vehicle accommodated? What routes will they take?
Response: A WB-50 is the largest vehicle that can be handled at the westerly U-turn, which would
exceed the largest expected vehicle. The current design of the east bow tie does not accommodate
trucks/buses as trucks are prohibited on the Arborway and the likelihood of trucks needing to use the
easterly u-turn is very low. The only potential route for trucks to use that u-turn would be from South
Street destined to Washington Street northbound. Those few trucks could utilize Ukraine Way to
complete this maneuver with the truck restriction in place.
Comment: How will trucks that miss the West Bow Tie be addressed as they drive westbound
on the Arborway?
Response: The Arborway will be signed to inform trucks to exit prior to or at the westerly U-turn.
Should a vehicle continue past errantly, they will be subject to enforcement, as under the existing
conditions.
Comment: Please review the left turn for transit buses at Casey Arborway/Washington St. How
many use this at peak? What happens when 3 to 4 buses arrive at the same time? Is the signal
length long enough for these buses? What happens when traffic is backed up from the bus
station's Lower Busway intersection? (see The Lower Busway at Forest Hills Station questions,
below)
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Response: The bus turn lane is long enough to accommodate at least three buses in queue. Two buses
can queue between the Casey Arborway and the lower busway. Under the existing Arborway Yard
configuration, 16 buses are schedule to make the left turn at the Casey Arborway/Washington Street
intersection in the morning peak hour. In the afternoon peak, there are 20 buses scheduled to make this
left turn. There are currently no deadhead buses making this left turn during the peak hours.
The MBTA was contacted with regards to the delays at the lower busway. The MBTA’s Superintendent
of Arborway Garage has been monitoring Forest Hills Station on a daily basis for quite some time. He
reviewed the pictures that were provided and said that these pictures are not a regular occurrence. On a
rare occasion there may be slight congestion in the street, but it is infrequent. We will continue to
monitor this situation to confirm if it occurs with any regularity.
Synchro Modeling Questions and Requests
Arborway/Washington Street 2016 at-grade intersection capacity calculations provided on last page.
Comment: We would like all traffic modeling to be posted for this project, if it is not already.
Response: The traffic analysis for a number of design iterations has been made available
throughout the planning and design stages of this project. The traffic analysis has been included
in the Functional Design Report that accompanies the 25% design. Specifically, the capacity
analysis reports are provided in Appendix F for existing conditions, Appendix I for Future NoBuild Condition, and Appendix K for the Build Condition.
Comment: Has a new Synchro traffic model been done with the reduced lanes version of the
Casey Arborway? If so, we would like to have access to it as soon as possible definitely prior to
our next DAG meeting. If a new model has not been run, why not?
Response: A preliminary Synchro analysis was developed to assess the feasibility of the reduced lane
configuration. The design is currently moving forward with 6 thru lanes as the full-build concept, which
is reflected in the 25% design documents. During the 75% design stage, the team will evaluate
alternatives for the opening year, including a reduced cross-section, and the traffic analysis will be further
refined. The analysis of alternative designs that are proposed for implementation will be made available.
If an alternative design is implemented for opening year, the location of features such as trees and
drainage structures will be based on the full-build design, to allow the future build-out to occur at a later
date with minimal changes.
Comment: If three lanes of thru traffic gives a Level of Service "D" won't reducing to two lanes
make the Level of Service worse? Please explain.
Response: The intent of the reduced lane alternatives is to minimize pedestrian crossing
distances and overall pavement area. The lane reductions do reduce overall traffic capacity and
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affect the associated operations. The options for reduced lane configurations are still being
evaluated and are not formally incorporated into the design at this time. Detailed analysis of the
reduced lane alternative will be developed and made available during the 75% design stage.
Comment: Is the Synchro modeling going to be run with the correct number of transit buses
utilizing the bus left turn lane on the Casey Arborway? Please explain.
Response: MBTA data of actual bus operations was reviewed extensively and the transit bus
volumes are correct in the current Synchro model and match the bus volumes counts. Graphics
illustrating scheduled bus volumes; actual bus volume counts; and deadhead bus volumes based
on the MBTA’s Automatic Vehicle Location (AVL) data are provided in the Functional Design
Report.
Comment: As currently modeled, the eastbound Casey Arborway traffic queue backs upstream
from Washington St across the South St. intersection. How will #39 transit buses negotiate the
backed up traffic to their special pullover. How will turning traffic turn into the backed up
traffic?
Response: Based upon 2035 peak hour conditions, the average queue on the Arborway EB is
less than 250 feet, which is not long enough to block South Street access to the Bus 39 lane. In
the current 25% design, the Bus 39 will be relocated to the Upper Busway, and therefore, the EB
bus lane on the Arborway is no longer required. The queues along the Arborway do not extend
to adjacent intersections, allowing space to store vehicles as they turn onto the Arborway.
Additional pre-cautions can be implemented as the design advances, such as queue detection
loops, to adjust signal timings to actively manage queue lengths.
Comment: The type of backups, noted just previously, also occur on the westbound Casey
Arborway from Washington St. upstream across the East Bow Tie. How will U-turning traffic
turn into the backed up traffic? Will backed up U-turn traffic block eastbound traffic?
Response: The average queues for 2035 volume (541 feet in the AM peak hour and 360 feet in
the PM peak hour) on the Arborway WB from the Washington Street/New Washington Street
intersection approach the U-turn intersection as the intersections are 500 feet apart. However,
the Arborway westbound movement operates at LOS C in the AM peak hour and LOS B in the
PM peak hour and any queuing is expected to clear each cycle. With the proposed signal
coordination, when the eastbound U-turning traffic is moving, the Arborway WB traffic will be
moving, allowing the queue to dissipate and avoid any potential blockage. The eastbound Uturn has ample storage space for vehicles in an exclusive turn lane, which will not block EB
traffic. The exclusive U-turn lane provides 260 feet of storage and the average queues are
projected to be 189 feet in the AM peak hour and 199 feet in the PM peak hour.
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Comment: The Synchro model was only run for 15 minutes of time. What happens to the
queue lengths when it is run for longer, more realistic, periods of time?
Response: The Synchro model is based on a one hour time period. The model applies a peak
hour factor, which uses the highest 15 minutes of traffic for each approach over the one hour
duration. As such, the analysis is conservative since it is based upon the worst 15 minutes of
traffic for each approach occurring simultaneously and continuing for the full one hour period.
Comment: At rush hour, vehicles will use Courthouse Frontage Road to avoid long queue
waiting to turn left at Forest Hill Drive. The Synchro model should include vehicles that will
take this alternate route.
Response: The volume of traffic turning left onto Forest Hill Drive in the peak hour is 587
vehicles in the AM and 580 vehicles in the PM peak hours. With the signal coordination
favoring the east-west movements at Shea Square, using the Frontage Road to avoid a left turn
on the Arborway will not result in a time savings. In addition, a second eastbound left-turn lane
has been included in the refined design and analysis per direction from the City of Boston. At
the Shea Square intersection, the proposed delays for the eastbound left are 44 seconds and the
delays for the northbound through are 48 seconds in the AM peak hour, and 16 seconds for the
eastbound left and 42 seconds for the northbound through in the PM peak hour. These delays
combined with the lower travel speeds on the Courthouse Frontage Road, make it unlikely that
anyone would use this route as a cut-thru.
Comment: We expect the East Bow tie and its pedestrian crossing to be included in Synchro
modeling. We would like access to this as soon as possible. Stopped traffic may queue across
the Casey Arborway/Washington Street intersection?
Response: The current Synchro analysis includes the pedestrian crossing at the easterly Uturn, and the average queues will not cross the adjacent intersection. The analysis is included in
the Functional Design Report, which is part of the 25% design submission.
Comment: The Synchro model shows left turn queues that are longer than the turn lanes.
Please explain.
Response: The available storage areas provided for all left turn lanes exceed the anticipated
50% queue lengths in the future peak periods. Refined analysis results, including the projected
queue lengths, is included in the Functional Design Report.
The Lower Busway at Forest Hills Station Questions and Requests
Comment: The lower busway at Forest Hills Station lacks the capacity to handle arriving peak
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hour buses. Excess buses overflow out of the station. On street “storage” is insufficient to
handle the overflow buses. This currently creates traffic backups from the Lower Busway
intersection back upstream across the new Washington St./Washington St. intersection. (This is
a capacity problem at the lower busway, not a signaling problem.) The Casey Arborway will
add an extra 28,000 cars on the surface roads, and will move the New Washington
St./Washington St. 125 feet closer to the Lower Busway intersection reducing on street “storage”
even more. Please review in depth how this traffic situation has been addressed and
eliminated.
Response: As stated previously, the MBTA was contacted with regards to the delays at the lower
busway. The MBTA’s Superintendent of Arborway Garage has been monitoring Forest Hills Station on
a daily basis for quite some time. He reviewed the pictures that were provided and said that these pictures
are not a regular occurrence. On a rare occasion there may be slight congestion in the street, but it is
infrequent. This situation will be monitored as the project proceeds.
Shea Square Comments and Requests
Comment: How was it decided that the Eggabout and the Shea Square proposals would work
as well or better than the existing Shea Rotary? Please provide all traffic modeling for this, and
explain the decision process in detail.
Response: In early WAG meetings, Shea Square was identified as a primary area of concern.
In addition, Shea Square is a high accident location and has deficient pedestrian and bicycle
accommodations. During a subsequent WAG meeting, the advantages and disadvantages of the
Shea scenarios were discussed in breakout groups and summarized with the entire group. The
general consensus was that the Eggabout did not adequately service pedestrians and bicyclists.
The high accident rate of the rotary was also cited as a significant concern.
Arborway/Washington Street 2016 At-Grade Intersection Capacity Calculations:
Comment:
Casey Arborway 2016 AM Rush Hours
1855 Westbound vehicles will need to cross the Arbor/Washington St. intersection per AM hour
MassDOT’s Synchro 7 Traffic Modeling says:
80 seconds per complete intersection signal cycle = 45 signal cycles per hour
Westbound AM Casey Arborway/Washington St green signal = 32 seconds
2 seconds of green signal allows 1 car to cross intersection. (truck and busses take longer)
Thus, 32 sec. of green signal allows 16 cars to cross intersection per lane
And 2 lanes allows 32 cars to cross intersection per signal cycle
And 45 signal cycles per hour at 32 cars per cycle allows 1440 cars per hour to cross the
intersection if 1855 vehicles need to cross and only 1440 can cross??????
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Response: The calculation shown is an over-simplification of the westbound capacity for the
given set of conditions. The capacity is based upon the number of lanes and the signal timings.
The signal timings are being refined. Based on currently proposed signal timings, the lane
group capacity for the WB thru-right is 2392 vehicles per hour, which exceeds the existing
volume and the 2016 volume cited in this comment.
Comment:
Casey Arborway 2016 PM Rush Hours
1759 Eastbound vehicles will need to cross the Arbor/Washington St. intersection per PM hour
MassDOT’s Synchro 7 Traffic Modeling says:
120 seconds per complete intersection signal cycle = 30 signal cycles per hour
Eastbound PM Casey Arborway/Washington St green signal = 54 seconds
2 seconds of green signal allows 1 car to cross intersection. (truck and busses take longer)
Thus, 54 sec. of green signal allows 27 cars to cross intersection per lane
and 2 lanes allows 54 cars to cross intersection per signal cycle and
30 signal cycles per hour at 54 cars per cycle allows 1620 cars per hour to cross the intersection
if 1759 vehicles need to cross and only 1620 can cross??????
Response: As stated in the previous comment, the calculation shown is an over-simplification
of the eastbound capacity for the given set of conditions. Based on currently proposed signal
timings, the lane group capacity for the EB thru-right is 2460 vehicles per hour, which exceeds
the existing volume and the 2016 volume cited in this comment.