Safety and Operations Analyses at Selected Intersections in Holbrook

RE Safety and Operations Analyses at Selected Boston Region MPO Intersections, FFY 2013: North/South Franklin Street (Route 37) at Union Street/Plymouth Street (Route 139) in Holbrook

1 INTRODUCTION

This memorandum summarizes safety and operations analyses and proposes improvement strategies for the intersection of North/South Franklin Street (Route 37) at Union Street/Plymouth Street (Route 139) in Holbrook.

The location was approved for study by the Boston Region MPO following a selection process for four locations from a short list of 21 intersections based on a series of criteria, including a high EDPO (Equivalent Property Damage Only) crash rating, the number of pedestrian and bicycle crashes, transit significance, regional significance, and implementation potential. 1

This intersection is ranked as 37 in the MassDOT’s 2008–10 statewide top 200 intersection crash list. The Town expressed a strong interest in studying the location for safety and operational improvements.

It also includes technical appendices that contain the methods and data that were applied in the study and detailed reports of the intersection capacity analyses.

2 EXISTING CONDITIONS

This location can be regarded as the most significant intersection in the town. It is located at the center of the town, where two major state routes, Route 37 and Route 139, meet. The intersection is under the Town’s jurisdiction.

Route 37, running in the north–south direction, is a principal arterial that begins in the north end of downtown Brockton. After crossing the Middleborough/Lakeville commuter rail line, it enters Holbrook. It winds through the town and intersects Route 139 at the town center. It then enters Braintree, passing through the town’s neighborhoods, Quincy Reservoir, and South Shore Plaza before ending at Interstate 93 (I-93) at Exit 6, just west of the Braintree Split. The section in Holbrook, known as North and South Franklin streets, contains two lanes, one lane in each direction, along most of that section.

Route 139, running in the east–west direction, is also a principal arterial. It begins in Stoughton Square at the southern junction of the Route 27 and Route 138 and heads northeast until its junction with Route 24. After briefly merging with Route 28 in Randolph, it heads east-southeasterly through Holbrook, the southwest corner of Weymouth, the north section of Abington, Rockland, Hanover, the northern edge of Pembroke, and Marshfield, where it connects to the section of Route 3 known as Pilgrims Highway, at Exit 12. The Route 139 section in Holbrook, known as Union Street, Plymouth Street, and Abington Avenue, contains two lanes, one lane in each direction, along most of that section.

Both state routes carry a high proportion of commuting traffic. As a result, traffic at this intersection is congested during the morning and evening peak hours. The Route 139 approaches are especially congested, due to heavy left-turn volumes and limited space for accommodating multiple through or turning lanes.

Figure 1 shows the existing intersection layout and the adjacent land uses. At the intersection, both streets widen to accommodate turning lanes. The Route 37 northbound approach (South Franklin Street) contains three 12-foot lanes, one for left turns, one for through movements, and one for right turns. The Route 37 southbound approach (North Franklin Street) contains a 12-foot left-turn lane and a 15-foot through and right-turn shared lane. Route 139 is narrower than Route 37 near the intersection. Both the eastbound (Union Street) and westbound (Plymouth Street) approaches contain two 11-foot lanes, one for left turns and one shared by through and right-turn movements. All of the streets contain narrow shoulders of less than 2 feet in width. All of the approaches are fairly level, except the slightly uphill eastbound approach (Union Street).

The adjacent areas are mainly public and commercial land uses. Holbrook Town Hall is located about 250 feet north of the intersection on the west side of North Franklin Street. Next to Town Hall, a small park known as the town green, resides on the northwest corner of the intersection. Holbrook Public Library is also located near the intersection, at the northeast corner, on Plymouth Street.

Commercial developments are mainly located on Route 37. Most prominently, a Walgreens Pharmacy and its parking lot are on the southeast corner of the intersection. North of the intersection, shops and restaurants, including a Tedeschi Food Shops store and Holbrook House of Pizza, are located on the west side of Route 37. South of the intersection, the Corner Grill and Pizzeria and a few retail shops and offices are located on the west side. Walgreens Pharmacy, an auto parts store, and a gas station are located on the east side. The only major commercial development on Route 139 is a Dunkin’ Donuts, located on Union Street just east of the town green. Farther away from the intersection, both sides of the two state routes are mainly residential.

There are sidewalks on both sides of Route 37 and Route 139. They are about 5 to 6 feet wide in most sections and about 8 to 10 feet wide at the corners of the intersection. Crosswalks are installed across all the approaches at the intersection. They are all equipped with wheelchair ramps and accessible pedestrian signals.

The intersection’s signal equipment appears to have been updated. The signal heads are supported by mast arms at appropriate heights and positions. The signal faces are furnished with black plates to reduce sun glare (Figures 2 and 3).

The pedestrian signals are equipped with a countdown function. When the pedestrian signals are actuated, they are operated in a 25-second exclusive phase (Figures 4 and 5).

Located at the center of the town, the intersection carries a fair number of pedestrian crossings daily. During the most recent traffic count, on November 14, 2012, staff observed about 10 to 15 pedestrian crossings in the peak hour of traffic and about 25 to 40 pedestrian crossings in the two-hour peak traffic

period. Crossings occurred in all directions. A high percentage (almost 50 percent) of them occurred on the crosswalk on the westbound approach (Plymouth Street), as it is near a Walgreen’s Pharmacy and the town library.

There are few bicycles going through the intersection in the peak traffic periods. During the recent traffic count, staff observed about four bicycles in each of the two-hour peak traffic periods. No specific directions can be identified as a favorable bike path from the low number.

Based on the counts, heavy vehicles (trucks and buses) shared about 3.5 percent and 2.5 percent of total entry traffic of the intersection in the AM and PM peak hour individually. These percentages are considered normal, and no specific turning movements are identified with a high truck demand.

The Massachusetts Bay Transportation Authority (MBTA) bus Route 230, running partly on Route 37 between Montello Commuter Rail Station in Brockton and Quincy Center Station, on the Red Line, goes through this intersection about four to five times during each of the AM and PM peak hours. There are bus stops on both sides of Route 37 north and south of the intersection. They are located about 100 to 150 feet from the intersection. The bus stops appear to be appropriately located, and the bus operations generally do not interfere with the intersection’s traffic operations.

3 Issues and Concerns

Two major issues, probably related, are identified for the intersection. First, it has a high number of crashes and a high percentage (more than 30 percent) of crashes that cause personal injuries. Second, the intersection is highly congested during the AM and PM peak hours, especially for the Route 139 approaches. During the peak hours, traffic frequently backs up for nearly half a mile in both directions.

Based on the field observations and crash and traffic data analyses, the issues and concerns for the intersection can be summarized as:

4 Crash Data Analysis

Table 1 summarizes the crash statistics at the intersection based on the MassDOT Registry of Motor Vehicles (RMV) 2006–10 crash data. On average, approximately 22 crashes occurred at the intersection each year. About 34 percent of the crashes resulted in personal injuries. The crash types consisted of 43 percent rear-end collisions, 25 percent angle collisions, 7 percent sideswipe collisions, 6 percent single-vehicle collisions, 5 percent head-on collisions, and 15 percent unknown.

In the five-year period, two crashes involved a pedestrian and three crashes involved a bicycle.

About 42 percent of the crashes occurred during peak periods, which indicates that many of the crashes are potentially related to stop-and-go traffic conditions at the intersection.

The crash rate is another effective tool for examining the relative safety of a location. Based on the crash data and the turning-movement counts collected recently by staff, the crash rate for this intersection was calculated as 2.12 (see Appendix A). 2 This is much higher than the average crash rate for signalized intersections in MassDOT Highway Division District 5, which is estimated to be 0.77. 3

Based on vehicle directions, crash locations, most harmful event, and other factors from the MassDOT RMV’s 2006–10 crash data, MPO staff identified, to the extent possible from the data available, the types and locations of the crashes and constructed a collision diagram for the intersection. The collision diagram does not include the data for 2006, as they lack descriptions of the involved vehicles’ actions (such as stopping, moving straight ahead, or turning) prior to the crashes.

The collision diagram (Figure 6) shows a wide range of the types of collisions that occurred at different locations of the intersection in the four-year period. Rear-end collisions occurred on all the approaches. Many of them (15 of the total 36 crashes) occurred on the westbound approach (Plymouth Street). 4 A number of left-turn crashes occurred at the intersection from different directions. Most noticeably, six of them involved a vehicle turning left from the westbound approaches. These left-turn crashes usually are more likely causing personal injuries than the rear-end crashes.

5 Intersection Capacity Analysis

Staff collected turning-movement counts at the intersection on Wednesday, November 14, 2012. The weather was cloudy and chilly, with no rain, during the counts. The data were recorded in 15-minute intervals during peak traffic periods in the morning, from 7:00 to 9:00, and in the evening, from 4:00 to 6:00.

The peak traffic hour in each of the two periods was then identified and the associated turning movements and pedestrian crossings were used for the intersection’s capacity analysis.

Figure 7 shows the observed vehicular turning-movement counts in the AM peak hour and the PM peak hour. The intersection carried about 2,640 vehicles in the AM peak hour, from 7:30 to 8:30, and about 2,560 vehicles in the PM peak hour, from 5:00 to 6:00 (see Appendix B for detailed 15-minute breakdowns for passenger vehicles, various heavy vehicles, pedestrians, and bicycles in the peak periods and the peak hours).

There were 25 and 41 pedestrians crossing the intersection during the two-hour AM and PM peak period, respectively. During each of the AM and PM peak hours, about 10 pedestrian crossed the intersection. A high percentage (almost 50 percent) of the crossings occurred on the crosswalk on the westbound approach (Plymouth Street). The crosswalk is adjacent to Walgreens Pharmacy and the town library.

Heavy vehicles accounted for about 3.5 percent of the total entering traffic in the AM peak hour and about 2.5 percent in the PM peak hour. The right-turn movement from Plymouth Street to North Franklin Street had the highest share of heavy vehicles—about 25 percent to 30 percent in the each peak hour. However, the total traffic volume of that turning movement is relatively low, at about 30 to 60 vehicles in each peak hour. Overall, the heavy-vehicle percentage at this intersection is in the normal range, and no specific movements have a high heavy-vehicle traffic volume. The heavy-vehicle percentages at individual approaches were used for the intersection capacity analysis.

Based on the counts and the manual traffic signal timing, the intersection was modeled as a fully actuated intersection. The signal cycle consists of the following phases: 1) protected/permissive left turn on Route 37, 2) all movements (left turns permissive) on Route 37, 3) protected-only left turn on Route 139, 4) through/right turn on Route 139, and 5) an on-call 25-second exclusive pedestrian signal phase. Table 2 summarizes the analysis results from applying Synchro to existing conditions in the AM and PM peak hours. 5

Street Name	Approach/Movement	LOS¹	Delay per Vehicle
Route 37	NB – Left	C (D)	33 (46)
Route 37	NB – Through	E (D)	59 (43)
Route 37	NB – Right	B (B)	16 (14)
Route 37	SB – Left	C (C)	31 (26)
Route 37	SB – Through/right	E (F)	56 (93)
Route 139	EB – Left	F (F)	90 (90)
Route 139	EB – Through/right	F (F)	95 (96)
Route 139	WB – Left	F (F)	110 (137)
Route 139	WB – Through/right	F (F)	165 (79)
Overall	Blank	F (E)	88 (76)

¹ LOS = level of service. The LOS for the AM peak hour is the first letter. The LOS for the PM peak hour is in parentheses.

The analysis indicates that the intersection operates at an undesirable level of service (LOS) of F in the AM peak hour, with an average delay of nearly one and a half minutes per vehicle. In the PM peak hour, the intersection is estimated to operate at LOS E, with an average delay of more than a minute per vehicle.

Both of the Route 139 approaches are estimated to operate at LOS F, with an average delay of more than one and a half minutes per vehicle in both the AM and PM peak hours. The westbound approach is estimated to endure an extensive delay of nearly two minutes per vehicle in the AM peak hour. The Route 37 approaches are estimated as operating at an acceptable level of service, with the exception of the southbound though movement. It is estimated as operating at LOS F, with an average delay of about one and a half minutes per vehicle in the PM peak hour.

The detailed analysis parameters and results for the AM and PM peak hours are in Appendix C.

6 Improvement alternatives

The intersection’s signal equipment appears to have been updated. In addition, the intersection layout is practically optimized, under the current geometry which is limited by the surrounding establishments. The intersection is located at the center of the town and needs to preserve the pedestrian friendly environment. These constraints leave limited options for improving the intersection’s traffic operations.

MPO staff tested a number of traffic signal alternatives with various layout modifications, including one with no changes. To simplify the analysis, this memo exhibits only two alternatives: one with no layout changes and one with a layout modification that would have noticeable operational improvements but have the least impact to the surroundings.

The existing signal phasing sequence was not altered, as it is considered appropriate for the existing intersection layout. The two alternatives are:

Tables 3 and 4 summarizes the capacity analyses for the two improvement alternatives in both the AM and PM peak hours. Using Synchro’s signal optimization function, staff identified that a cycle length of 150 seconds, including an exclusive 25-second pedestrian signal phase, is appropriate for both alternatives.

Alternative 1, retiming the signal with a reduced cycle length, would improve the overall level of service and reduce delays somewhat, especially for the westbound lane movements. 6 In addition, the reduction of cycle length is also beneficial to pedestrians because they would have a shorter wait for the traffic cycle to terminate than in the existing signal setting.

Alternative 2, adding one more left-turn lane on the westbound approach, would reduce the approach delay noticeably. However, it would have a significant impact on the surroundings. The negative impacts include land takings on both sides of Route 139 on both the north and south of the intersection, longer and less safe crossings for pedestrians, the loss of two on-street parking spaces on the southbound side of North Franklin Street to accommodate double receiving lanes, and potential land taking on the curbside of the two receiving lanes for the two-lane section to gradually taper into one lane. 7 Because of these impacts, this alternative is not recommended.

Detailed signal timing settings and analysis results for the two alternatives in both the AM and PM peak hours are shown in Figure 8, Table 5, and Appendices D and E.

Intersection Capacity Analysis of Level-of-Service for
Existing Conditions and Alternatives

Blank	Blank	Existing Conditions	Alternative 1	Alternative 2
Street Name	Approach	LOS¹	LOS	LOS
Route 37	NB – Left	C (D)	E (E)	E (E)
Route 37	NB – Through	E (D)	E (D)	E (D)
Route 37	NB – Right	B (B)	B (B)	B (B)
Route 37	SB – Left	C (C)	E (C)	E (C)
Route 37	SB – Through/right	E (F)	E (F)	E (E)
Route 139	EB – Left	F (F)	F (F)	F (F)
Route 139	EB – Through/right	F (F)	E (F)	D (E)
Route 139	WB – Left	F (F)	F (F)	E (E)
Route 139	WB – Through/right	F (F)	F (F)	F (E)
Overall	Blank	F (E)	E (E)	E (E)

¹LOS = level of service. The LOS for the AM peak hour is the first letter. The LOS for the PM peak hour is in parentheses.

Intersection Capacity Analysis of Delay for
Existing Conditions and Alternatives

Blank	Blank	Existing Conditions	Alternative 1	Alternative 2
Street Name	Approach	Delay¹	Delay	Delay
Route 37	NB – Left	33 (46)	62 (64)	62 (63)
Route 37	NB – Through	59 (43)	62 (38)	62 (37)
Route 37	NB – Right	16 (14)	14 (10)	16 (12)
Route 37	SB – Left	31 (26)	58 (26)	58 (25)
Route 37	SB – Through/right	56 (93)	57 (82)	58 (75)
Route 139	EB – Left	90 (90)	97 (87)	97 (87)
Route 139	EB – Through/right	95 (96)	69 (92)	52 (66)
Route 139	WB – Left	110 (137)	92 (122)	68 (79)
Route 139	WB – Through/right	165 (79)	102 (67)	102 (72)
Overall	Blank	88 (76)	71 (68)	67 (60)

¹ The delay for the AM peak hour is the first number. The delay for the PM peak hour is in parentheses.

Intersection Signal Timings and Phasing for
Existing Conditions and Alternatives

Blank	Blank	Existing Conditions	Alternative 1	Alternative 2
Street Name	Approach	Phase	Phase	Phase
Route 37	NB – Left	5	5	5
Route 37	NB – Through	2	2	2
Route 37	NB – Right	2	2	2
Route 37	SB – Left	1	1	1
Route 37	SB – Through/right	6	6	6
Route 139	EB – Left	7	7	7
Route 139	EB – Through/right	4	4	4
Route 139	WB – Left	3	3	3
Route 139	WB – Through/right	8	8	8
Pedestrian	All	9	9	9

7 RECOMMENDATIONS AND DISCUSSION

The study intersection has a high number of crashes and is very congested during the peak hours, especially on the Route 139 approaches. The above analyses indicate that more than 40 percent of the crashes are potentially related to the congested conditions at the intersection.

Nevertheless, the congestion at the intersection is not easy to mitigate. Two major state routes in the region, Route 37 and Route 139, meet at this intersection. Both routes carry a high proportion of commuting traffic. Traffic at the intersection is frequently congested during the morning and evening peak hours. The Route 139 approaches are especially congested, as there are very few alternative east–west routes in the region.

Meanwhile, the intersection is located at the center of the town, near Town Hall, Holbrook Public Library, the town green, and many commercial developments, with significant pedestrian activity. The intersection’s signal equipment appears to be updated, and the layout is appropriate for its current signal operations. Pedestrian facilities, sidewalks, crosswalks, wheelchair ramps, and countdown and accessible pedestrian signals are all appropriately installed and need to be preserved.

These existing conditions leave almost no options for reducing the congestion through intersection layout modifications. The alternatives that involve intersection modifications, including one with double left-turn lanes on Route 139 (Alternative 2 in the last section), are all considered to have significant negative impacts to the surrounding land uses and are not recommended. The signal retiming alternative with no layout changes (Alternative 1 in the last section) is estimated to somewhat improve the operations on Route 139 and reduce the overall intersection delay.

In the short term, staff recommended Alternative 1, with the following considerations:

Currently the intersection provides sufficient pedestrian accommodation but no bicycle accommodation. Sharrow markings on the curb lane of all approaches could be considered.

In the long term, the following modifications should be considered when they can be incorporated into future Route 139 and Route 37 reconstruction and resurfacing projects:

1 Mark Abbot and Chen-Yuan Wang, memorandum to Boston Region MPO, “Safety and Operations Analyses at Selected Intersections—FFY 2013, Task 1: Intersection Selection Procedure,” November 1, 2012

2 Crash rates estimates are based on crash frequency (crashes per year) and vehicle exposure (traffic volumes or miles traveled). Per MassDOT guidance, crash rates are expressed as “crashes per million entering vehicles” for intersections and as “crashes per million miles traveled” for roadway segments.

3 The average crash rates estimated by the MassDOT Highway Division (as of January 23, 2013) are based on a database that contains intersection crash rates submitted to MassDOT as part of the review process for an Environmental Impact Report or Functional Design Report.

4 Sometimes the high number of rear-end crashes at an intersection is caused by insufficient signal clearance time. However, the intersection’s 5-second yellow, plus the all-red clearance time, is considered sufficient for all approaches.

5 Synchro Version 8 is developed and distributed by Trafficware Ltd. The software can perform capacity analysis and traffic simulation (when combined with SimTraffic software, also produced by Trafficware Ltd.) for an individual intersection or a series of intersections.

6 Manual signal timings performed in the field estimated the existing total cycle length to be about 180 seconds.

7 To align the travel lanes for safe operations, the modifications would extend beyond the east side of Route 139 to the west side of Route 139 for a substantial distance. In addition, the departure lanes on Route 37 would need to be widened somewhat to accommodate the new turning paths.

8 A review of the crash data indicates that nearly 80 percent of the crashes involving in injuries occurred in the off-peak hours. This indicates that approaching vehicles might have been traveling fast when the intersection was not congested. Currently the posted speed limits on all of the approaches within about 500 feet of the intersection are 25 mph. Frequent enforcement could raise drivers’ awareness of the speed limit.

9 The recently available MassDOT RMV 2011 crash data show that the intersection had eight crashes (two of them causing injuries) in that year, which is less than in previous years. Overall, the number of crashes at this intersection has been decreasing.

10 Currently the lane carries the heaviest left turns at the intersection but is the shortest of all the approaches. It can store only about 5 to 6 cars. Left-turning cars usually are stuck in the traffic queue and cannot move up in time for the left-turn signal phase.

Crash rates for the intersection are shown on MassDOT’s Intersection Crash Rate worksheet.

Four pages of tables. The counts cover “all vehicles,” cars, MBTA buses, trucks, and large trucks (freight), for various time periods.

AM and PM Peak-Hour Intersection Capacity Analysis: Alternative 1: Retiming Traffic Signal.

AM and PM Peak-Hour Intersection Capacity Analysis: Alternative 2: Doubling Left-Turn Lanes on Route 139.