McMAHON ASSOCIATES
300 Myles Standish Boulevard | Taunton, MA 02780
p 508-823-2245 | f 508-823-2246
www.mcmtrans.com
PRINCIPALS
Joseph W. McMahon, P.E.
Joseph J. DeSantis, P.E., PTOE
John S. DePalma
William T. Steffens
Casey A. Moore, P.E.
Gary R. McNaughton, P.E., PTOE
ASSOCIATES
MEMORANDUM
TO:
Steve McLaughlin, MassDOT
FROM:
Gary McNaughton, P.E., PTOE
SUBJECT:
Casey Overpass Project – Alternatives Analysis
DATE:
October 18, 2011
John J. Mitchell, P.E.
Christopher J. Williams, P.E.
John F. Yacapsin, P.E.
Introduction
This memorandum has been prepared to summarize the analysis of proposed alternatives for
the Casey Overpass project. The information contained within this memorandum will be
presented to the Working Advisory Group (WAG) and the public.
The extensive study area includes eighteen intersections along major roadways in the vicinity of
the Casey Overpass as depicted in Figure 1. The traffic highlights of the existing conditions at
the study area intersections have been posted on the project website, along with the projected
2035 traffic volumes.
Congestion is experienced on the existing street network during peak periods. Based on
existing conditions analysis, field observations, and discussions with the community, traffic
operations within this study area are affected by queue spill back between closely spaced
intersections, pick‐up/drop‐off conflicts in the vicinity of the MBTA Forest Hills Station, and
poor signal coordination. These factors negatively affect the overall operations at several key
intersections in the study area under existing conditions. The vehicular congestion deteriorates
conditions for other modes of traffic in the study area, as pedestrians, bicyclists, and transit‐
users are affected by the vehicular delays, excessive queues, and blocked throughways.
A multi‐modal traffic analysis has been conducted on the Casey Overpass alternatives, which
assesses operations for pedestrians, bicycles, transit (buses), and vehicular traffic. Specifically
for the New Washington Street corridor, an urban facility analysis was performed for the
existing and proposed conditions. The main intersections included on this corridor are the
intersections with South Street and with Washington Street/Hyde Park Avenue. The
methodology for analyzing an urban facility is primarily based on the 2010 Highway Capacity
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Steve McLaughlin October 18, 2011 Page 2 DRAFT Manual (HCM) and incorporates the four modes of transportation that exist along the corridor: pedestrian, bicycle, transit, and automobile modes. For vehicular traffic operations, in addition to conducting traffic capacity analyses at the study area intersections, queue analyses were conducted and travel time matrices were prepared for the existing condition and the proposed alternatives (At‐Grade and Single Bridge). Proposed Alternatives The development of the proposed alternatives for the Casey Overpass Project was based upon preliminary traffic analysis, urban design goals, and public input. The alternatives were broken down into two main types, at‐grade or bridge replacement alternatives. A number of possibilities were explored for each type of alternative through the public process, and a preferred alternative for an at‐grade and a bridge option were selected. The preferred alternatives are referred to as the “At‐Grade Medium Median Bow‐Tie” and the “Single Bridge” alternative. These alternatives are described in greater detail below. The at‐grade alternative consists of eliminating the bridge and servicing the traffic on surface roads. After consideration of a number of design options through the public process, the bow‐
tie intersection concept emerged as the preferred at‐grade alternative. The bow‐tie concept eliminates the eastbound and westbound left‐turns at the signalized intersections of New Washington Street/South Street and New Washington Street/Hyde Park Avenue. The elimination of the left‐turn movement on New Washington Street simplifies overall intersection operations and provides additional green time for the mainline Arborway through movements and the heavy north‐south movements along South Street and Hyde Park Avenue. The restricted left turn movements are directed to median U‐turns, to be constructed along the Arborway, east of Hyde Park Avenue and west of South Street, where vehicles can reverse their travel direction and then complete their originally intended maneuver by means of a right turn. The at‐grade alternative is depicted in Figure 2. The single bridge alternative consists of a new single structure providing one travel lane in each direction and aligned north of the existing bridge and over the center of the proposed New Washington Street alignment. As part of the bridge alternative, the surface street network is improved with a realignment of the corridor to improve overall roadway connection with minor geometric and signal timing changes proposed to the at‐grade intersections within the study area. The single bridge alternative is depicted in Figure 3 of this memorandum. Both of the alternatives were designed in order to minimize or eliminate some of the deficiencies in the existing network configuration, including queue spillback, pick up/drop off conflicts and poor signal coordination. Under the proposed alternatives, the street network has been reorganized and simplified. Traffic operations throughout the network are maintained or improved due to better signal coordination and updated traffic signal timings. AT-GR ADE
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Casey Overpass Project
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Casey Overpass Project
Steve McLaughlin October 18, 2011 Page 3 DRAFT Urban Street Facilities Analysis Methodology The Highway Capacity Manual 2010 (HCM) was released earlier this year with an improved methodology for the evaluation of the service provided to road users along an urban street. An urban street facility is defined as “a length of roadway that is composed of contiguous urban street segments and is typically functionally classified as an urban arterial or collector street.” A key element in the new methodology is the evaluation of multiple transportation modes along the same street including pedestrians, bicycles, transit, and automobile users. The urban street facility analysis is a performance based analysis in which the level‐of‐service (LOS) evaluation is based on each user type’s individual criteria. An urban street facility consists of a number of segments, each consisting of an intersection and a roadway link. The combination of analysis performed for each intersection and link create a level‐
of‐service for an urban facility. The section below discusses each mode’s criteria and basic methodology for the evaluation of service along an urban street. The non‐automobile modes considered in the HCM urban streets analysis include pedestrian, bicycle and transit modes. Utilizing the HCM methodologies, a LOS score is calculated by mathematically combining various performance measures and roadway characteristics. The calculated scores are then compared to the LOS Criteria for non‐automobile roadway users and a LOS is established for the intersection, segment or facility. Input data required for the analysis of pedestrians, bicycle and transit users overlaps between the three modes. The required input data for these modes can be found in Exhibit 17‐6 of the HCM which is included below. The values for the data elements listed in Exhibit 17‐6 have been observed, calculated or estimated based on engineering judgment and guidance from the HCM as part of this analysis process. Below is a brief description of the methodology for performance evaluation of the three non‐
automobile modes on an urban street facility. Steve McLaughlin October 18, 2011 Page 4
DRAFT
Input Data Requirements: Non‐Automobile Modes1 Pedestrians The two main performance evaluation criteria for pedestrians along an urban street facility are pedestrian space and pedestrian travel speed. The pedestrian LOS for the urban street facility accounts for all of the intersection and segments along the roadway. The pedestrian LOS score for an intersection is calculated for each crosswalk and is based on crossing distance, adjacent traffic volume, as well as the delay incurred by the average pedestrian arriving at the 1
Highway Capacity Manual 2010. Transportation Research Board, Washington, D.C.. 2010. National Academy of Sciences. Steve McLaughlin October 18, 2011 Page 5 DRAFT intersection. The segment LOS is then calculated for each side of the street and is mainly based on amount of space within the pedestrian walkway, travel speed and crossing difficulty. The pedestrian analysis combines a number of factors in order to calculate a pedestrian LOS score for an urban facility. Many of these factors deal with the pedestrian’s perception. For example, there are factors for the buffer width between the pedestrian and moving traffic, the speed of moving traffic, the number of travel lanes, the presence of fixed objects within the sidewalk, and the presence of on‐street parking adjacent to pedestrians. The factors have been developed based upon national studies. While the analysis includes many detailed factors, the difference between the pedestrians’ amenities in the project alternatives often did not result in a significant variation in the pedestrian LOS score. As a hypothetical example, the difference between a 5‐foot and a 6‐foot sidewalk does not affect the pedestrian LOS score substantially if the 5‐foot sidewalk provides adequate sidewalk space for the number of pedestrians under the given conditions. Therefore in some cases, little or no change is shown when analyzing each of the proposed alternatives and consideration outside of the LOS analysis should be taken. In addition to the LOS analysis, measures of evaluation (MOEs) have been developed in order to account for the additional amenities proposed as part of the at‐grade and bridge alternatives. The MOEs will be applied to the alternatives later in the public process. Bicycles The main performance measure for bicycles along an urban street is the travel speed of bicycles through the facility and travel space provided for the cyclists. The bicycle LOS for the urban street facility is based on delay incurred at boundary intersections as well as the ability to travel freely on the roadway segments. The bicycle LOS score at an intersection is calculated for each approach. The LOS score is based on crossing distance, presence of bicycle facilities, adjacent traffic volumes and the amount of green time in the cycle that is given to each bicycle approach. The segment LOS is calculated for each direction of travel on the street, based on the same factors as the intersection LOS as well as the number of access points on the side of roadway for the analyzed direction of travel, the presence of on‐street parking, the percentage of heavy vehicles, the pavement condition, and traffic volumes and speeds. The urban facilities analysis considers bicycle facilities provided on the roadway (i.e. bicycle lanes). Recognizing that both of the proposed alternatives provide off street bicycle facilities, we note that the urban facility results do not reflect the off‐street bicycle facilities and the benefits of these off‐street amenities will be considered elsewhere in the evaluation of the alternatives. Transit The main performance measure for transit users along an urban street is transit travel speed. For this project, transit consists of the various bus routes accessing Forest Hills Station. The transit LOS for the urban street facility accounts for all of the intersections and segments along the roadways. The transit LOS score for an intersection is calculated for the approach on which Steve McLaughlin October 18, 2011 Page 6 DRAFT the transit service arrives. The segment LOS is based on delay incurred at the boundary intersections, travel speed along the roadway, pedestrian LOS for the adjacent walkway, and the transit wait‐ride score. The transit wait‐ride score is based on transit headways and perceived travel time. New Washington Street Urban Facility Analysis Results In order to compare operations and performance for existing conditions, the at‐grade alternative, and bridge alternative, the urban facility analysis methodologies described above were applied to the New Washington Street corridor. The New Washington Street analysis corridor is defined as the portion of Arborway/New Washington from west of its intersection with South Street to east of its intersection with Washington Street/Hyde Park Avenue. For the purpose of this analysis, Segment 1 is defined as the portion west of South Street, Segment 2 is defined as the roadway between South Street and Washington Street/Hyde Park Avenue and Segment 3 is the portion of road east of Washington Street/Hyde Park Avenue. Discussed below are the pedestrian, bicycle and transit operations according to the urban facility analysis methodologies described above. Pedestrian Mode As described above, the pedestrian LOS is mainly based on pedestrian space and pedestrian travel speed along an urban facility. In order to obtain an urban facility LOS for pedestrians, space and travel speed calculations were conducted at the corridor intersections, roadway links and segments on each side of the facility. The pedestrian LOS for each of these components is depicted in Figure 4, Figure 5 and Figure 6 for the existing, at‐grade and bridge alternative traffic conditions. Pedestrian LOS for intersections is calculated for each crosswalk, while pedestrian LOS for roadway links and segments are calculated for each side of the roadway. As shown in Figure 4, the pedestrian LOS for the facility is LOS C under the existing conditions during the weekday morning and weekday afternoon peak hours. All of the intersection crosswalks are shown to perform at LOS B or better and all of the segments are shown to perform at LOS C during both peak hours. The pedestrian LOS were not calculated for the north side of Segment 1 or the south side of Segment 3 due to the lack of pedestrian facilities on these portions of the roadway under existing conditions. The pedestrian analysis shows a good level of performance of the existing infrastructure due to the existing sidewalks widths and crosswalk connections. However, there are missing crosswalk connections that are not affecting the LOS results. These missing links are assessed in other evaluation criteria and measures of effectiveness. The pedestrian LOS for the at‐grade alternative are depicted in Figure 5, below. As shown, the LOS of the crosswalks at the intersections is shown in some cases to be slightly worse than existing conditions. The LOS at the intersection crosswalks are all expected to perform at LOS C or better during both of the peak hours with the exception of the western sidewalk at the intersection of New Washington and South Street which is expected to operate at LOS D during South Street
SCHEMATICNOT TO SCALE
LOS C/C
LOS C/C
New Washington Street
LOS C/C
Hyde Park
Avenue
LOS C/C
Casey Overpass Study
FIGURE 4
Pedestrian LOS
Existing AM and PM Peak Hours
Boston, Massachusetts
Legend
Intersection LOS
LOS A/B
LOS D
A.M. P.M.
Link LOS
LOS C
Segment LOS
A.M.
LOS X/X
P.M.
LOS E/F
South Street
SCHEMATICNOT TO SCALE
LOS C/C
LOS C/C
LOS C/C
New Washington Street
LOS C/C
LOS B/B
Hyde Park
Avenue
LOS C/C
Casey Overpass Study
FIGURE 5
Pedestrian LOS
At-Grade Alternative AM and PM Peak Hours
Boston, Massachusetts
Legend
Intersection LOS
LOS A/B
LOS D
A.M. P.M.
Link LOS
LOS C
Segment LOS
A.M.
LOS X/X
P.M.
LOS E/F
South Street
SCHEMATICNOT TO SCALE
LOS C/C
LOS C/C
New Washington Street
LOS C/C
LOS C/C
Hyde Park
Avenue
LOS C/C
Casey Overpass Study
FIGURE 6
Pedestrian LOS
Bridge Alternative AM and PM Peak Hours
Boston, Massachusetts
Legend
Intersection LOS
LOS A/B
LOS D
A.M. P.M.
Link LOS
LOS C
Segment LOS
A.M.
LOS X/X
P.M.
LOS E/F
Steve McLaughlin October 18, 2011 Page 7 DRAFT both peak hours. The pedestrian LOS at the intersections have degraded slightly due to the change in pedestrian phasing from exclusive phasing to concurrent phasing. This change affects the analysis in that vehicles (specifically permitted left turns, since right turn on red will be restricted) will be crossing over the crosswalk at the same time as pedestrians and therefore negatively impacting the LOS. The impacts at the crosswalks are minor and the pedestrian analysis does not account for the time savings gained from concurrent pedestrian phasing. Each of the segment LOS have been maintained at LOS C under the at‐grade alternative and the inclusion of pedestrian facilities on the south side of Segment 3 provide LOS B during both the weekday morning and weekday afternoon peak hours. Under the at‐grade alternative, the pedestrian facilities along the New Washington corridor are expected to operate at LOS C during both of the peak hours. As discussed above, there are additional pedestrian elements proposed as part of the proposed alternatives that are not accounted for within this pedestrian analysis, but are considered elsewhere in the alternatives evaluation. These include the off‐
street multi‐use paths and the improved pedestrian amenities along Washington Street. Figure 6 depicts the pedestrian LOS under the bridge alternative and shows that operations for pedestrians along the corridor are expected to be generally comparable to the at‐grade alternative; however, all crosswalks experience LOS C or better. Similar to the at‐grade alternative, additional pedestrian improvements are proposed under this alternative for other roadways and off‐street. These additional improvements are not accounted for within this urban facility analysis and ought to consider elsewhere in the evaluation of the alternatives. Bicycle Mode Bicycle LOS along the Arborway corridor was calculated for the South Street and Hyde Park Avenue intersections and the roadway segments in both directions of travel before and after each intersection. Each individual bicycle LOS is depicted in Figure 7, Figure 8 and Figure 9 for the existing, at‐grade and bridge alternatives. Bicycle analysis was conducted for both the weekday morning and weekday afternoon peak hours. Figure 7 depicts the bicycle levels‐of‐service along the New Washington Street corridor under existing traffic volumes. As seen in the figure, all but Segment 3 operate at LOS D or better during both the weekday morning and weekday afternoon peak hours. Segment 3 is shown to operate at LOS E during both peak hours for the eastbound and westbound directions of travel. At the intersections of New Washington Street with South Street and with Hyde Park Avenue, the northbound and southbound bicycle movements operate at LOS D or worse during both peak hours. The overall poor level‐of‐service along the corridor can be attributed to a number of factors at both the intersection and segment levels of analysis. The two biggest contributing factors are the lack of bicycle lanes or other facilities and the high delay experienced by the bicycles traveling along the New Washington Street corridor. The westbound direction of Segment 1 is operating a LOS C during both peak hours due to a wider travel lane and lower traffic volumes, allowing more space for bicycles within the roadway. The overall bicycle LOS Steve McLaughlin October 18, 2011 Page 8 DRAFT for the facility is LOS D for both the eastbound and westbound directions of travel during the weekday morning and weekday afternoon peak hours. Figure 8 shows the bicycle LOS for the at‐grade alternative. The individual intersection LOS are improved to LOS B or better over the existing conditions except for the westbound movement at the eastern bow‐tie signal, which is shown to operate at LOS C during the weekday morning peak hour. The improvements at the intersections are mainly based on inclusion of a bicycle lane on all of the New Washington Street approaches and the Washington/Hyde Park Avenue approaches. The LOS on the South Street approaches improves because the distance across the intersection is decreased. All of the segment levels‐of‐service are expected to be maintained or improved to LOS C during both the weekday morning and weekday afternoon peak hours except for the Segment 3 eastbound direction, which shown to be maintained at LOS D. Segment 3 in the eastbound direction does not show a drastic improvement in LOS due to the access point on the south side of the roadway and the presence of the eastern bow‐tie traffic signal, both of which limit LOS improvement under the at‐grade alternative. The overall bicycle LOS for the facility is expected to be LOS C for both the eastbound and westbound directions of travel during the weekday morning and weekday afternoon peak hours with the at‐grade alternative. The bicycle levels‐of‐service for the bridge alternative are shown to be similar to the bicycle LOS of the at‐grade alternative, as these alternatives have similar bicycle amenities. No bicycle lanes are proposed for the northbound approach at Hyde Park Avenue and therefore, the LOS for that approach is only shown to be LOS C during both the weekday morning and weekday afternoon peak hours. Under the bridge alternative, Segment 3 also is expected to operate at LOS D during both peak hours for the eastbound and westbound directions due to the two access points on each side of the roadway, affecting the LOS score. The bicycle LOS for the facility is shown to be LOS C for the eastbound and westbound directions of travel during both weekday peak hours with the bridge alternative. Transit Mode Both the at‐grade and bridge alternatives propose to alter the route of the MBTA Route 39 bus. In order to determine how the route change affects the Route 39 general operations, transit urban facility analysis has been conducted for the existing, at‐grade and bridge alternatives. Although the path of the Route 39 bus is to change under the at‐grade and bridge alternatives, the transit LOS remains unchanged. The transit LOS along this corridor for the Route 39 bus is shown to be LOS C during both time periods and under all three traffic conditions. The travel time through the corridor is the only varying component between the existing conditions and the proposed alternatives, and that change in delay is not significant enough to change the transit LOS for this facility. Note that the project alternatives include improvements to other MBTA bus routes, particularly as it relates to the Washington Street access to/from Forest Hills Station. These improvements are not considered in this urban facility analysis since they are South Street
SCHEMATICNOT TO SCALE
LOS D/D
LOS C/C
LOS E/E
New Washington Street
LOS D/D
LOS E/D
Hyde Park
Avenue
LOS D/D
Casey Overpass Study
FIGURE 7
Bicycle LOS
Existing AM and PM Peak Hours
Boston, Massachusetts
Legend
Intersection LOS
LOS A/B
LOS D
A.M. P.M.
Link LOS
LOS C
Segment LOS
A.M.
LOS X/X
P.M.
LOS E/F
South Street
LOS C/C
Western Bow Tie
LOS C/C
LOS C/C
Eastern Bow Tie
SCHEMATIC­
NOT TO SCALE
New Washington Street
LOS C/C
LOS D/D
Hyde Park
Avenue
LOS C/C
Casey Overpass Study
FIGURE 8
Bicycle LOS
At-Grade Alternative AM and PM Peak Hours
Boston, Massachusetts
Legend
Intersection LOS
LOS A/B
LOS D
A.M. P.M.
Link LOS
LOS C
Segment LOS
A.M.
LOS X/X
P.M.
LOS E/F
South Street
SCHEMATICNOT TO SCALE
LOS C/C
LOS C/C
LOS D/D
New Washington Street
LOS C/C
LOS D/D
Hyde Park
Avenue
LOS C/C
Casey Overpass Study
FIGURE 9
Bicycle LOS
Bridge Alternative AM and PM Peak Hours
Boston, Massachusetts
Legend
Intersection LOS
LOS A/B
LOS D
A.M. P.M.
Link LOS
LOS C
Segment LOS
A.M.
LOS X/X
P.M.
LOS E/F
Steve McLaughlin October 18, 2011 Page 9 DRAFT not located along New Washington Street and will be considered elsewhere it the evaluation of the alternatives or in subsequent transit analysis. Vehicular Traffic Analysis The vehicular traffic analysis conducted for the Casey Overpass study area is three‐fold and includes intersection capacity analysis, queue analysis and travel time matrices. Intersection capacity and queue analyses were conducted for the study area intersections to evaluate vehicle operations for the at‐grade and bridge traffic alternatives during the weekday morning and weekday afternoon peak hour. Based on a review of the traffic data under the existing conditions, the weekday morning peak hour of the study area network traffic occurs from 7:15 AM to 8:15 AM and the weekday afternoon peak hour is shown to occur between 5:00 PM and 6:00 PM. Existing traffic volumes were projected to the year 2035 based on the CTPS regional model and local development projections. Peak hour traffic volumes for the 2035 at‐grade and 2035 bridge alternatives are included in the appendix of this memorandum for the weekday morning and weekday afternoon peak hours, respectively. Traffic analysis for the existing conditions and the traffic volume projections for the 2035 build year have been discussed in previous meetings of the Working Advisory Group. Based on the methodologies from the 2000 Highway Capacity Manual, detailed capacity/level‐of‐
service analyses were completed for the projected 2035 peak hour volumes at the study area intersections. Level‐of‐service (LOS) is a term used to describe the quality of traffic flow on a roadway or intersection for a particular point in time. For intersection analyses, level‐of‐service (LOS) is a measure of vehicle delay. Operating levels of service are reported on a scale of A to F with A representing little or no delay and F representing longer delays. LOS D is generally considered acceptable in this region and LOS E and F may be acceptable for certain movements. The full capacity analysis results for the at‐grade and bridge alternatives are summarized in the appendix of this memorandum and the overall LOS for each intersection during the weekday morning and weekday afternoon peak hour are shown in the table below, for the at‐grade and bridge traffic conditions. Steve McLaughlin October 18, 2011 Page 10
DRAFT
Overall Future Vehicular Traffic Operations ‐ Signalized Intersections
At‐Grade Alternative
Morning Peak Hour
1
2
3
Bridge Alternative
Afternoon Peak Hour
Morning Peak Hour
Afternoon Peak Hour
LOS
Delay
V/C
LOS
Delay
V/C
LOS
Delay
V/C
LOS
Delay
V/C
South Street/New Washington Street/Ramps
D
48.7
1.03
D
37.1
0.92
C
27.9
0.89
E
60.8
1.00
South Street/Washington Street/MBTA Busway
E
63.7
0.86
D
36.5
0.84
D
39.2
0.90
D
49.0
0.89
Washington Street at Ukraine Way
C
24.0
0.82
D
49.5
0.95
C
27.1
0.83
D
49.7
0.95
Hyde Park Avenue at Walk Hill Street
C
26.1
0.91
C
29.7
0.94
C
25.5
0.84
C
30.1
0.94
Hyde Park Avenue at Ukraine Way
D
51.7
1.11
C
34.0
0.90
D
45.3
1.06
C
30.2
0.88
Washington Street at Tower Street
A
9.7
0.58
A
9.1
0.60
B
14.1
0.55
A
7.1
0.61
Washington Street at Fitzgerald Lot
A
3.0
0.44
A
4.3
0.56
A
4.9
0.43
A
6.3
0.56
Washington Street at New Washington Street
C
22.9
1.02
C
31.2
1.00
D
40.3
0.97
C
32.2
0.89
Arborway at Eastern Bow‐Tie
B
14.2
1.01
B
11.6
0.70
n/a
n/a
n/a
n/a
n/a
n/a
Arborway at Western Bow‐Tie
A
7.2
0.65
C
30.6
0.92
n/a
n/a
n/a
n/a
n/a
n/a
Intersection
1
Level‐of‐Service
2
Average vehicle delay in seconds
3
Volume to capacity ratio
Under the at‐grade and bridge alternatives, all of the signalized intersections in the project study area are shown to operate at an overall LOS D or better, except for the intersections of South Street/New Washington/Arborway Ramps (LOS E under the bridge alternative during the weekday afternoon peak hour) and South Street/ Washington Street (LOS E under the at‐
grade alternative during the weekday morning peak hour). Due to the projected increase in traffic throughout the study area network, there are also a number of capacity restraints where the volume‐to‐capacity (v/c) ration is greater than 1.0, indicating that the traffic volume is greater than the theoretical capacity for that movement. As shown in the table above and the attached appendix, the traffic operations for both the at‐grade and bridge alternatives are shown to maintain or improve traffic operations over the existing conditions. In addition to the traffic capacity analysis, queue analyses for the at‐grade and bridge alternatives were conducted. As discussed previously, queue spill back between study area intersections is a concern, specifically at the two New Washington Street intersections as well as the intersection of Washington Street and South Street. The queuing analysis results are included in a summary table located in the appendix to this memorandum. As shown in this queue summary, the improvements of the proposed alternatives better manage queues between these intersections. The results of the traffic analyses will be presented in detail at subsequent WAG and public meeting and is documented in the appendices of this memorandum. Steve McLaughlin October 18, 2011 Page 11
DRAFT
Travel Time Analysis Overall, the proposed alternatives improve travel times in the study area over the existing street network. The particular design features of each alternative shorten and lengthen particular movements. To quantify the differences in travel time, matrices have been prepared to compare travel routes in the study area between six identified zones of the study area, as seen in Figure 10. Travel times between each of the zones have been calculated based on the delay and travel times identified in the capacity analysis. The travel times for the existing traffic conditions, the at‐grade alternative, and the bridge alternative are shown below for the weekday morning and afternoon peak hours. Existing - AM
Travel Time in Minutes
(destination)
A
(origin)
A
B
C
D
E
F
4.9
0.3
5.5
6.4
0.8
0.5
2.1
3.0
3.4
1.4
2.3
2.7
0.8
0.5
B
0.6
C
1.0
0.9
D
2.1
2.0
2.0
E
1.8
1.7
1.7
0.9
F
0.8
3.2
3.2
1.9
1.1
2.0
Existing - PM
Travel Time in Minutes
(destination)
A
(origin)
A
B
C
D
E
F
1.7
2.8
2.2
3.1
0.8
0.7
2.1
2.4
2.7
1.3
2.2
2.5
0.4
0.6
B
0.8
C
0.9
0.8
D
2.2
2.0
2.1
E
2.2
2.0
2.0
0.8
F
0.8
3.1
3.2
1.5
1.1
1.5
Travel Time Comparison
A
B
E
Origins/Destinations
A
Arborway
B
South @ St Marks
C
Washington St @ Forest Hills Station
D
Hyde Park Ave @ Forest Hills Station
E
Washington St @ Arborway Yard
F
Shea Circle
F
C
D
Steve McLaughlin October 18, 2011 Page 12
DRAFT
At-Grade Alternative - 2035 AM
Travel Time in Minutes
(destination)
A
(origin)
A
B
C
D
E
F
2.7
0.6
1.1
2.2
1.3
0.6
1.1
2.2
1.3
3.3
4.4
3.5
0.9
1.0
B
0.8
C
0.8
2.8
D
1.0
0.9
1.6
E
1.4
1.2
1.9
0.7
F
1.9
1.8
2.5
3.1
0.8
1.3
At-Grade Alternative - 2035 PM
Travel Time in Minutes
(destination)
A
(origin)
A
B
C
D
E
F
4.2
1.2
2.1
3.7
2.4
1.2
1.1
2.7
1.3
1.2
2.8
1.5
0.8
1.0
B
1.4
C
1.0
0.6
D
1.7
1.5
3.3
E
2.0
1.9
3.7
1.3
F
1.8
1.7
3.5
4.5
1.0
1.2
Steve McLaughlin October 18, 2011 Page 13
DRAFT
Bridge Alternative - 2035 AM
Travel Time in Minutes
(destination)
A
(origin)
A
B
C
D
E
F
0.8
0.5
1.3
1.8
0.8
0.4
1.2
1.3
1.4
1.6
2.1
1.7
1.0
0.6
B
0.5
C
0.9
0.7
D
1.4
1.2
1.2
E
1.2
1.0
1.0
0.7
F
0.8
2.5
2.4
1.8
0.9
1.8
Bridge Alternative - 2035 PM
Travel Time in Minutes
(destination)
A
(origin)
A
B
C
D
E
F
0.5
1.5
2.3
2.6
0.8
0.9
1.8
2.0
2.0
2.3
2.6
2.5
0.7
0.5
B
1.1
C
1.6
1.5
D
1.7
1.6
2.3
E
1.1
1.0
1.7
0.8
F
0.8
2.4
2.9
1.6
1.0
1.7
In comparing the travel times of the bridge alternative to the existing conditions travel times, a majority of the movements experience a shortened travel time. In most cases, the travel time difference is less than one minute, which is not likely perceptible to the average driver over the course of their trip. None of the movements increase in travel time by more than one minute. Travel time savings as high as four minutes are realized by movements originating at A and destined to B, D, and E. These time savings are attributed to the reorganization of the grade level street network. In comparing the travel times of the at‐grade alternative to the existing travel times, approximately half of the movements experience shorter travel times and half experience longer travel times. Most of these increases and decreases are less than one minute and therefore, not Steve McLaughlin October 18, 2011 Page 14 DRAFT discernable to the average driver. The movements traveling from Zone C to Zone E and Zone F to Zone D under the at‐grade alternative are shown to have longer travel times through the network, as expected, since these movements are made via the bow‐tie U‐turns. However, it is likely that vehicles will avoid the added travel of the U‐turn by utilizing Ukraine Street to access Hyde Park Avenue or Washington Street, depending on their final destination point. Other movements with slightly longer travel times under the at‐grade alternative during the weekday morning peak hour are mainly vehicles traveling north and west, which are the peak movements during this time period. Likewise, during the afternoon peak hour the longer travel times are for the peak movements, eastbound and southbound. Next Steps This memorandum presented the existing and future operations based on the urban facilities LOS analysis. This type of performance evaluation provides an overall traffic operation assessment for all roadway users, including pedestrian, bicycle and transit users. These analysis results will be considered and incorporated into the evaluation of the proposed alternatives.