Memorandum

Date:    January 9, 2013

To:         Boston Region Metropolitan Planning Organization

From:   Seth Asante, MPO Staff

Re:         Traffic Signal-Retiming Study for Route 2 in Concord and Lincoln

1         executive summary

This study provided sufficient information to assess the signal-timing issues in the Route 2 corridor caused by reconstruction of the Route 2, Route 2A, and Cambridge Street intersection. The analysis presented herein—along with the existing construction and permit jobs—will become part of a coordinated effort to improve traffic flow throughout the corridor. The traffic signal-retiming strategy would improve traffic flow over the short term, and would function only during the construction stage. After construction is complete, traffic flows would readjust to reflect changes in the highway network; and the MPO staff believes that post-construction traffic signal retiming should be conducted to reflect these changes.

MassDOT and the Boston Region Metropolitan Planning Organization (MPO) collected or provided operational, geometric, and safety data to evaluate existing and retimed conditions. The six signalized intersections were retimed in the corridor. Staff developed two new timing plans for this study: Option 1 consists of retiming and coordinating the existing traffic signal system; while Option 2 involves installing geometric improvements in addition to the retiming and coordinating.

This memorandum is organized into six sections:

1.1      Findings of Analysis

2         background and scope of work

The arterial segment of Route 2 in Concord and Lincoln was selected for study because the Boston Region MPO’s LRTP identified Route 2 as one of the priority arterial segments in need of maintenance, safety, and mobility improvements. This segment was a high priority for improvement for MassDOT Highway Division District 4 because of serious congestion and safety issues. To help identify solutions for addressing problems in priority arterial segments, an arterial segment study was included in the federal fiscal year (FFY) 2013 Unified Planning Work Program (UPWP).1

2.1      Study Area and Purpose

The approximately 5.5-mile study area is comprised of Route 2 from the Baker Avenue Extension in Concord to Bedford Road in Lincoln (Figure 1). The purpose of this study was to retime six traffic signals in the study area in order to improve traffic operations on Route 2 during reconstruction of the intersection of Route 2, Route 2A, and the Cambridge Turnpike at Crosby Corner (Figure 1). Construction, which began in spring 2012 and should end in spring 2016, is expected to affect traffic flow on Route 2 in Concord and Lincoln. At the time of this writing, mitigation work, such as erosion control, relocation of utility lines and poles, excavation, and pothole repair is underway. The study also examined the effects of the retiming on traffic flow in the arterial segment. MPO staff conducted this study, working closely with the MassDOT Highway Division District 4.

We excluded the Route 2, Route 2A, and Cambridge Turnpike intersection from this study based on discussions with MassDOT Highway Division, as this intersection is currently under construction. This is only one section in the entire study area. In addition, the Concord Rotary, located on the western end of the study area (Figure 1), was excluded from the study because a proposed project would replace the existing Concord Rotary with a highway interchange. Presently, Concord Rotary traffic queues affect traffic on Route 2, particularly in the vicinity of the Route 2 and Baker Avenue Extension intersection.

2.2      Scope of Work

The project’s work included data collection, assessment of existing conditions, and development of new timing plans and improvements. MassDOT and MPO staff collected the data; MPO staff conducted the assessment of existing conditions and developed new timings. The six intersections whose traffic signals were retimed are, from east to west (Figure 2):


FIGURE 1 is a map that depicts the study 5.5-mile study area comprised of Route 2 from the Baker Avenue Extension in Concord to Bedford Road in Lincoln.

 


Figure 2 is a combination of maps and aerial photos that show the six intersections on Route 2 whose traffic signals were retimed.

 

3         data collection

Data used to evaluate existing conditions and develop new timing plans was either collected in the field or obtained from other sources such as MassDOT traffic signal and crash databases. The data collected included:

4         Evaluation of Existing Conditions

It was important to understand existing traffic characteristics within the study area—including number and rates of crashes, delays, and queues—prior to developing new timing plans.

4.1      Roadway

Route 2 is under the jurisdiction of MassDOT and generally runs in an east-west direction (Figure 1). It is functionally classified as a principal arterial roadway. Route 2 is part of the national highway system (NHS), and as such is a federal-aid-eligible roadway. In the study area, Route 2 has two travel lanes in each direction—and exclusive turn lanes—which are wider at the signalized intersections. The posted speed limit on Route 2 is 45 miles per hour (mph), from the Bedford Road intersection in Lincoln to the Baker Avenue Extension intersection in Concord. Route 2 has 6- to 8-foot shoulders on both sides of the roadway, and for the most part, a median barrier; however, the section between Sandy Pond Road and Oak Knoll Road has no shoulder or median. There are no sidewalks or bicycle lanes on Route 2.

4.2      Intersections

The major intersections on Route 2 are controlled by traffic signals. Figure 2 shows the configuration of the six signalized intersections that were studied. Here, crosswalks and pushbutton pedestrian signals have been installed and are functioning well. The minor intersections in the study area are controlled by stop signs on side streets, where only right-turning movements are permitted. Pedestrians are prohibited from crossing Route 2 at unsignalized intersections that contain a median barrier.

4.3      Traffic, Pedestrian, and Bicycle Volumes

The three locations of the ATR counts on Route 2 are cited below and displayed in Figure 3.

Based on the ATR counts, the average weekday daily traffic volumes range between 41,000 and 51,000 vehicles. The TMCs also are summarized in Figure 3. The TMCs do not reflect the traffic queues or traffic demand at the intersections because only vehicles that pass through the intersections were counted—vehicles already in queue at the end of counting period were not counted. This situation occurs because congestion and queues on Route 2 last significantly longer than the periods during which the TMCs were conducted. Estimates of the average number queued vehicles were determined during field visits. See Table 1 for the percentage of heavy vehicles at study intersections during peak periods when the TMCs were conducted. The table indicates that this percentage ranges between 2.0 and 3.0 percent, which is not particularly high for peak-period traffic conditions. Also, staff did not detect any roadway geometry—such as turning radii—that would inhibit truck traffic flow.

The percentage of heavy vehicles was higher on Main Street and Old Road to Nine Acre Corner compared to the other cross streets. This study did not investigate the reasons for the high percentage of heavy vehicles here because it was not study’s focus.

There were few pedestrians crossing Route 2 at the study intersections during peak periods (Table 2).

 

Figure 3 is a map plus diagrams that indicate the locations of the existing turning-movement volumes on Route 2.

 

 

 

TABLE 1
Percentage of Heavy Vehicles at Intersections during AM and PM Peak Periods

 

Intersection and Approach

Percentage of Heavy Vehicles

Route 2 at Bedford Road:

--

Route 2 EB

2.2%

Route 2 WB

2.1

Bedford Road NB

1.4

Bedford Road SB

1.0

Route 2 at Walden Street (Route 126):

--

Route 2 EB

2.6%

Route 2 WB

2.5

Walden Street NB

1.8

Walden Street SB

2.0

Route 2 at Sudbury Road:

--

Route 2 EB

2.8%

Route 2 WB

2.5

Sudbury NB

2.0

Sudbury SB

2.4

Route 2 at Old Road to Nine-Acre Corner:

--

Route 2 EB

2.6%

Route 2 WB

2.3

Old Road to Nine-Acre Corner NB

3.5

Old Road to Nine-Acre Corner SB

5.8

Route 2 at Main Street:

--

Route 2 EB

2.8%

Route 2 WB

2.6

Main Street NB

5.8

Main Street SB

8.1

Route 2 at Baker Avenue Extension:

--

Route 2 EB

2.7%

Route 2 WB

2.9

Baker Avenue Extension NB

2.0

Baker Avenue Extension SB

1.7

Note: The AM peak period is 7:00 AM to 9:00 AM and the PM peak period is 4:00 PM to 6:00 PM.

Source: Central Transportation Planning Staff.

 

TABLE 2
Pedestrian and Bicycle Counts at the Study Intersections

 

Intersection

AM Peak Period Pedestrian Crossings

PM Peak Period Pedestrian Crossings

AM Peak Period Bicycle Counts

PM Peak Period Bicycle Counts

Route 2 at Bedford Road

0

0

0

0

Route 2 at Walden Street (Route 126)

2

0

0

0

Route 2 at Sudbury Road

1

2

0

0

Route 2 at Old Road To Nine-Acre Corner

1

1

0

0

Route 2 at Main Street

0

2

0

0

Route 2 at Baker Avenue Extension

0

1

0

1

Note: The AM peak period is 7:00 AM to 9:00 AM; the PM peak period is 4:00 PM to 6:00 PM.

Source: Central Transportation Planning Staff.

4.4      Crash Data

MPO staff used crash data obtained from the MassDOT Registry of Motor Vehicles (RMV) to evaluate safety at the study intersections. The RMV crash data cover the period from January 2006 through December 2010. For details of crashes—severity, manner of collision, and ambient light conditions—at each of the study intersections, see Table 3. The average crash rates were calculated per MassDOT’s methodology. The District 4 Highway Division’s average crash rate (published by MassDOT based on crash information queried on January 23, 2013) is 0.77 crashes per million entering vehicles at signalized intersections. Four of the study intersections have crash rates greater than or equal to the District 4 average for signalized intersections:

At each of these four intersections, the most prevalent crash type was rear-end collisions. The majority of crashes occurred on Route 2 rather than on the cross streets. The high number of rear-end collisions on Route 2 appears to result from unexpected stops because of traffic queues at the signalized intersections and high travel speeds. (See Appendix C for collision diagrams and crash-rate worksheets.)


 

TABLE 3
Crash Summaries and Rates for Study Intersections (2006–2010)

 

Characteristic

Route 2 at

Bedford Road

Route 2 at

Walden Street

Route 2 at

Sudbury Road

Route 2 at Old Rd to Nine Acre Corner

Route 2 at Main Street

Route 2 at Baker Avenue Extension

Fatal Injury

0

0

0

0

0

1

Non-Fatal Injury

27

27

16

7

36

22

Property Damage Only

55

55

30

23

83

26

Unknown/Not Reported

4

7

3

2

5

0

Angle

17

5

6

10

14

18

Rear-End

47

70

38

15

91

25

Sideswipe

4

7

2

2

8

2

Single-Vehicle Crash

13

5

6

8

5

2

Head-On Collision

1

0

1

0

1

2

Unknown/Not Reported

3

3

1

0

4

0

Pedestrians

0

0

0

2

0

0

Bicyclists

0

0

0

0

1

0

AM or PM Peak Period*

31

31

23

15

41

20

Non-Peak Period

55

58

31

18

83

29

Dry

66

74

48

29

80

41

Wet or Icy

20

16

9

4

44

8

Daylight

72

81

46

24

100

44

Dark (Lit or Unlit)

14

9

8

9

21

4

Total Crashes

86

90

54

33

124

49

5-Year Average

18

18

11

7

25

10

Crash Rate

0.85

0.91

0.61

0.42

1.53

0.77

Note: Shading denotes intersections with crash rates higher than Highway Division District 4 average crash rate.

Source: Central Transportation Planning Staff.

4.5      Traffic Operations

Using the data collected, plus observed conditions in the field, MPO staff built a network for the AM and PM peak periods using Synchro Studio 8 traffic software. The TMC data, existing phases and sequences, network offsets, and phase intervals and splits were input to a model determined to the arterial levels of service (LOS), delays, and queues at the signalized intersections. LOS and capacity analyses were conducted on the 2012 existing conditions and calibrated to the observed operating conditions to provide a baseline scenario.

Two time settings were evaluated for existing conditions—AM and PM peak periods. No consideration was given for special events or weekend timing because there are no shopping malls or major sports facilities in the Route 2 corridor—the primary cause of congestion was high traffic volume resulting from commuter work trips.

Analyses were conducted in a manner consistent with the Highway Capacity Manual (HCM) 2010 methodology, which expresses the quality of driving conditions at signalized intersections it in terms of LOS ratings A through F:

Based on the Highway Division’s existing signal-timing plan, traffic signals at the following intersections operate with coordination during peak periods:

Traffic signal coordination occurs when a group of two or more traffic signals are working together so that cars moving through the group will make the least number of stops possible. In order for this to happen, each traffic signal in the group must allow a green light for all directions of travel during a fixed time period. Coordination operations are in effect during the morning peak period from 6:30 AM to 9:30 AM and during the evening peak period from 3:00 PM to 7:00 PM. The coordinated cycle lengths are 110 seconds for the AM peak period and 120 seconds for the PM peak period. The coordinated traffic signal system uses a global positioning system (GPS) timer to keep the traffic signals perfectly synchronized.

Traffic signals at the intersections of Route 2 and Walden Street and Bedford Road operate alone; they are not coordinated because of the long distances between them and the other signals.

4.5.1   Operating Problems

MPO staff observed the following operating conditions in the field:

  1. During the AM peak period, long traffic queues develop on the Route 2 eastbound approaches at the signalized intersections.
  2. Similarly, during the PM peak period, long traffic queues develop on the Route 2 westbound approaches at the signalized intersections.
  3. Some of the side streets experience long queues, and it appears that not enough green times are allocated to the side streets, especially at:

  4. During peak periods, left-turn queues on Route 2 at the Main Street and Baker Avenue Extension intersection extend into the main travel lanes, interrupting traffic flow.
  5. Tables 4 and 5 below present results of the intersection-capacity analysis for the existing conditions in terms of LOS, delays, and queues. The analysis shows that the signalized intersections are operating at or above capacity during peak periods. The analysis also indicates long queues on Route 2 and some of the side streets during peak periods. (See Appendix D for LOS analysis worksheets.)
  6. At the signalized intersections, there are no bicycle detection devices on the side streets to help bicyclists cross Route 2. There also are no bicycle pavement markings or signs on the approaches of the side streets to let bicyclists know how to cross Route 2.  

 

5         Development OF New Timing Plans

MPO staff developed two timing plans and compared them with the existing timing plans put in place by MassDOT Highway Division District 4.

 

TABLE 4
AM Peak-Hour Level of Service

Approach

Movement

Existing

LOS

Existing Delay1

Existing Queue2

Option 1 LOS

Option 1 Delay

Option 1 Queue

Option 2 LOS

Option 2 Delay

Option 2 Queue

Route 2 EB

T

F

117

#1443

F

138

#1523

F

136

#1572

Route 2 EB

R

A

5

0

A

6

0

A

6

0

Route 2 WB

T

B

12

494

B

15

562

B

15

562

Route 2 WB

R

A

5

0

A

6

0

A

6

0

Bedford St. NB

L+T

D

45

#306

D

42

#291

E

101

#261

Bedford St. NB

R

A

0

0

A

0

0

A

0

0

Bedford St. SB

L+T

F

>180

#863

F

>180

#855

--

--

--

Bedford St. SB

L*

--

--

--

--

--

--

F

> 180

#368

Bedford St. SB

T*

--

--

--

--

--

--

E

72

#291

Bedford St. SB

R

A

0

0

A

0

0

A

0

0

Overall

All

F

117

--

F

114

--

F

91

--

Route 2 EB

L

E

55

27

E

67

28

E

67

28

Route 2 EB

T

F

110

#1334

F

170

#1269

F

170

#1269

Route 2 EB

R

A

6

51

A

10

39

A

10

39

Route 2 WB

L

E

55

99

F

83

#124

F

83

#124

Route 2 WB

T

A

9

561

B

17

514

B

17

514

Route 2 WB

R

A

4

22

A

8

21

A

8

21

Walden St. NB

L

D

42

#161

E

60

#188

E

60

#188

Walden St. NB

T

D

47

#184

F

92

#226

F

92

#226

Walden St. NB

R

A

0

91

A

0

0

A

0

0

Walden St. SB

L

F

>180

#395

F

>180

#449

F

>180

#449

Walden St. SB

T

F

>180

216

D

43

228

D

53

228

Walden St. SB

R

A

0

0

A

0

0

A

0

0

Overall

All

F

103

--

F

107

--

F

107

--

Route 2 EB

L

D

51

m13

D

55

m14

D

54

m14

Route 2 EB

T

F

168

m#1044

F

149

m#1057

F

149

m#1057

Route 2 EB

R

B

11

m0

B

10

m0

B

10

0

Route 2 WB

L

E

55

#167

E

73

#219

E

73

#219

Route 2 WB

T

B

17

589

B

16

589

B

16

589

Route 2 WB

R

A

8

0

A

7

0

A

7

0

Sudbury Rd. NB

L+T+R

F

128

#445

F

152

#445

--

--

--

Sudbury Rd. NB

T+L*

--

--

--

--

--

--

D

39

126

Sudbury Rd. NB

R*

--

---

--

--

--

---

D

40

235

Sudbury Rd. SB

L+T+R

F

180

#589

F

>180

#415

--

--

--

Sudbury Rd. SB

L*

--

--

--

--

--

--

D

46

96

Sudbury Rd. SB

T+R*

--

--

--

--

--

--

D

41

146

Overall

All

D

109

--

F

104

---

F

86

--

Route 2 EB

L

D

49

m44

D

54

m51

D

54

m52

Route 2 EB

T

D

37

m131

C

16

m154

C

16

m207

Route 2 EB

R

A

0

m0

A

0

m0

A

0

m4

Route 2 WB

L

D

58

m129

E

67

m149

E

67

m164

Route 2 WB

T+R

C

16

m228

B

14

m248

B

14

252

Old Rd to Nine Acre Rd NB

L

E

58

#165

E

62

#165

E

62

#165

Old Rd to Nine Acre Rd NB

T

D

53

#315

E

57

#315

E

57

#315

Old Rd to Nine Acre Rd NB

R

D

36

206

D

38

215

D

38

215

Old Rd to Nine Acre Rd SB

L

D

51

39

D

53

39

D

53

37

Old Rd to Nine Acre Rd SB

T+R

D

43

207

D

45

207

D

45

207

Overall

All

D

32

--

C

24

--

C

24

--

Route 2 EB

T

F

>180

#977

F

117

#888

E

71

#843

Route 2 EB

R

A

0

m0

A

0

m0

A

0

0

Route 2 WB

L

D

50

m#327

E

>180

m#481

E

75

m#215

Route 2 WB

T

B

12

310

B

11

272

B

12

240

Route 2 WB

R

A

0

m0

A

0

0

A

0

0

Main St NB

L+T

F

82

#550

F

94

#562

F

82

#550

Main St NB

R

A

0

m0

A

0

0

A

0

0

Main St SB

L+T+R

D

37

165

D

38

167

D

37

165

Overall

All

F

123

--

F

82

--

D

52

--

Route 2 EB

L

D

55

#546

E

64

#583

E

64

#583

Route 2 EB

T

A

13

390

B

12

313

B

12

313

Route 2 EB

R

A

1

23

A

0

18

A

0

18

Route 2 WB

T

D

60

m#741

D

48

m#626

D

49

m#618

Route 2 WB

R

A

0

m29

A

0

m17

A

0

m21

Baker Ave. Extension NB

L+T

D

48

120

D

52

143

D

52

#143

Baker Ave. Extension NB

R

D

39

0

D

      42

0

D

      42

0

Baker Ave. Extension SB

L

D

50

14

D

54

15

D

54

15

Baker Ave. Extension SB

T+R

D

42

127

D

45

135

D

45

135

Overall

All

D

37

--

D

35

--

D

35

--

*Geometric improvement.

1 Delay in seconds per vehicle.

2 95th percentile queue length in feet.

# means that the 95th percentile volume exceeds capacity. m means upstream metering is in effect.

Source: Central Transportation Planning Staff.

TABLE 5

PM Peak-Hour Level of Service

 
Approach Movement Existing LOS Existing Delay1 Existing Queue2 Option 1 LOS Option 1 Delay Option 1 Queue Option 2 LOS Option 2 Delay Option 2 Queue
Route 2 EB T B 14 467 B 13 467 B 13 467
Route 2 EB R A 7 52 A 7 52 A 7 52
Route 2 WB T F 112 #1378 F 112 582 F 112 #1378
Route 2 WB R F 83 24 F 107 -- F 107 24
Bedford St. NB L+T D 43 #342 D 43 #342 F >180 #312
Bedford St. NB R A 0 0 A 0 39 A 0 0
Bedford St. SB L+T F >180 #898 F >180 #884 -- -- --
Bedford St. SB L* -- -- 0 -- -- -- E 152 #277
Bedford St. SB T* -- -- -- -- -- -- D 90 467
Bedford St. SB R R A 0 A 0 0 A 0 0
Overall All F 104 -- F 103 -- F 96 --
Route 2 EB L E 72 68 E 73 70 E 72 70
Route 2 EB T B 16 551 B 19 667 B 16 630
Route 2 EB R A 7 18 A 8 22 A 7 20
Route 2 WB L F 102 #224 E 77 #167 E 77 #183
Route 2 WB T D 36 #1209 D 45 #1256 D 35 966
Route 2 WB R A 6 24 A 6 23 A 6 27
Walden St. NB L F 92 #208 E 70 #185 E 76 #208
Walden St. NB T F 81 #292 E 63 #254 F 83 #292
Walden St. NB R A 0 10 A 0 0 A 0 0
Walden St. SB L F 174 #197 F 90 #180 F 153 #196
Walden St. SB T E 56 154 E 53 150 E 57 154
Walden St. SB R A 0 4 A 0 4 A 0 4
Overall All C 34 -- C 36 -- C 33 --
Route 2 EB L E 60 m45 E 65 m50 E 67 m54
Route 2 EB T F 120 m#798 F 82 m#917 D 39 m#885
Route 2 EB R B 18 m0 B 15 m0 B 13 0
Route 2 WB L E 57 #439 F 87 #475 E 72 #457
Route 2 WB T F 92 #1205 E 72 #1089 C 30 #884
Route 2 WB R A 9 0 A 8 0 A 6 0
Sudbury Rd. NB L+T+R D 52 252 E 60 #293 -- -- --
Sudbury Rd. NB T+L* -- -- -- -- -- -- D 57 #187
Sudbury Rd. NB R* -- -- -- -- -- --- C 31 99
Sudbury Rd. SB L+T+R E 57 #328 E 78 #365 -- -- --
Sudbury Rd. SB L* -- -- -- -- -- -- E 55 69
Sudbury Rd. SB T+R* -- -- -- -- -- -- E 58 #266
Overall All F 95 -- E 76 -- D 38 --
Route 2 EB L E 56 m31 E 59 m29 E 60 m34
Route 2 EB T C 22 m#869 D 43 m434 C 25 m818
Route 2 EB R A 0 m22 A 0 m9 A 0 m0
Route 2 WB L D 52 m158 E 58 m167 E 55 m92
Route 2 WB T+R E 70 m#912 D 43 m#918 D 47 #1024
Old Rd to Nine Acre Rd NB L E 53 #186 E 74 #204 E 60 #204
Old Rd to Nine Acre Rd NB T D 39 168 D 44 175 D 43 175
Old Rd to Nine Acre Rd NB R C 27 94 C 31 105 C 35 105
Old Rd to Nine Acre Rd SB L D 43 55 D 49 58 D 47 58
Old Rd to Nine Acre Rd SB T+R D 41 221 D 48 231 D 46 231
Overall All D 47 -- D 44 -- D 39 --
Route 2 EB T E 40 #675 E 73 #791 C 31 #646
Route 2 EB R A 0 m0 A 0 m0 A 0 m0
Route 2 WB L F 174 m#530 E 74 m#494 D 52 m198
Route 2 WB T B 16 m41 B 16 m417 B 17 m57
Route 2 WB R A 0 m0 A 0 m1 A 0 m0
Main St NB L+T D 51 #338 D 51 #338 D 46 290
Main St NB R A 0 101 A 0 101 A 0 107
Main St SB L+T+R E 65 #444 E 65 #444 D 55 #396
Overall All D 49 -- D 49 -- D 31 --
Route 2 EB L E 75 #262 E 89 #307 E 75 #262
Route 2 EB T B 13 360 B 13 360 B 12 338
Route 2 EB R A 0 14 A 0 14 A 0 14
Route 2 WB T E 67 #898 E 59 #880 E 55 #835
Route 2 WB R A 0 m21 A 0 m8 A 0 m13
Baker Ave. Extension NB L+T E 75 #392 E 80 #401 E 64 #410
Baker Ave. Extension NB R D 36 30 D 36           30 D 37 30
Baker Ave. Extension SB L E 63 30 E 62 30 E 62 30
Baker Ave. Extension SB T+R D 37 133 D 37 135 D 39 136
Overall All D 46 -- D 44 -- D 40 --

* Geometric improvement

1 Delay in seconds per vehicle.

2 95th percentile queue length in feet.

# means that the 95th percentile volume exceeds capacity. m means upstream metering is in effect.

Source: Central Transportation Planning Staff.

5.1      Option1: Retiming and Coordinating of Existing Traffic Signal System

Option 1 consists of retiming and coordinating the existing traffic signal system using the methodology discussed earlier. For safety, enough time was allocated for pedestrians to cross Route 2 or a side street from curb to curb. Known as the “pedestrian clearance interval,” this is represented by the flashing DON'T WALK or upraised-hand signal. As with pedestrian crossings, adequate time was allocated for cross-street and left-turning traffic.

5.2      Option 2: Geometric Improvements and Retiming and Coordination

Option 2 consists of geometric improvements in addition to the signal retiming and coordination described in Option 1. Proposed new construction entails:

Tables 4 and 5 below present results of the intersection-capacity analysis for the two options in terms of LOS, delays, and queues. (See Appendix D for the LOS analysis worksheets for the two options.)

There appears to be enough space in the right-of-way for constructing these geometric improvements. For each of these, a 200-foot turn lane would be sufficient to improve traffic operations. In addition, they each would require new traffic signal heads to control the turn lane. These improvements would cost between $500,000 and $750,000, except for the second westbound left-turn lane on Route 2 at Main Street, which would cost between $750,000 and $1.0 million.

5.3      Time-of-Day Signal Settings

The final component to the new timing plan is the time-of-day signal settings. These settings determine the optimal timing plan for each hour of a typical weekday. The time-of-day signal settings were obtained by evaluating the 24-hour ATR count data from three locations on Route 2. (See Appendix E for signal settings for the peak- and off-peak periods.) The peak-period operations are:

5.4      Measures of Effectiveness

To measure the effectiveness of the timing plans, Synchro 8 was used to evaluate arterial LOS—in terms of delay, travel time, and speed—for the two options described above. (See Table 6 below.)

TABLE 6

Route 2 Signal-Retiming Results: Arterial Levels of Service

Scenario

Total Signal Delay (Minutes)

Change in Signal Delay (%)

Total Travel Time (minutes)

Change in Travel Time (%)

Arterial Speed (MPH)

Change in Arterial Speed (%)

Arterial
LOS

AM Eastbound Route 2:

--

--

--

--

--

--

--

Existing Condition

10.6

--

18.6

--

18

--

D

Option 1

9.3

-12

17.1

-8

19

+5

D

Option 2

9.0

-15

16.6

-10

20

+11

D

AM Westbound Route 2:

--

--

--

--

--

--

--

Existing Condition

2.7

--

10.8

--

33

--

B

Option 1

2.4

-11

10.5

-3

34

+3

B

Option 2

2.3

-15

10.4

-4

35

+6

B

PM Eastbound Route 2:

--

--

--

--

--

--

--

Existing Condition

3.5

--

11.0

--

30

--

C

Option 1

3.1

-11

10.6

-4

31

+3

B

Option 2

2.8

-20

9.8

-11

34

+13

B

PM Westbound Route 2:

--

--

--

--

--

--

--

Existing Condition

10.1

--

18.1

--

18

--

D

Option 1

9.2

-9

17.3

-4

19

+5

D

Option 2

8.4

-17

16.5

-9

20

+11

D

LOS = Level of service.

Source: Central Transportation Planning Staff.

6.        Recommendations

Short-Term Solution:

  1. MPO staff recommends Option 1, retiming and coordination of the existing traffic signal system, to alleviate congestion in the Route 2 corridor for the near term. (See Appendix F for Option 1 Timing plans.)
  2. Install bicycle detection devices, pavement markings, and signs to help bicyclists cross Route 2 at the signalized intersections.

Medium-Term Solution:

  1. MPO staff recommends that MassDOT Highway Division District 4 consider Option 2, geometric improvements and retiming and coordination for the medium term.

  2. Regarding Option 2, analysis shows benefits would be realized from the following construction:

SAA/saa

cc:  M. Karas, MassDOT District 4
J. Onorato, MassDOT District 4   C. Raphael, MassDOT District 4 P. Nelson, MassDOT Planning

 

Figures

  1. Study Area
  2. Study Intersections
  3. Existing Turning Movement Counts and Average Daily Traffic

Appendixes

A. Turning Movement and Automatic Traffic Recorder Counts
B. Existing Signal-Timing Information
C. Crash Rate Worksheets and Collision Diagrams
D. Level of Service Analyses
E. Time of Day Signal Settings
F. Timing Plan for Option 1—Retiming and Coordination of Existing Traffic Signals

 

1 Boston Region Metropolitan Planning Organization, Unified Planning Work Program, Federal Fiscal Year 2013, Endorsed by the Boston Region Metropolitan Planning Organization on June 28, 2012.