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
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:
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
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.
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):
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:
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.
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.
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.
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).
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.
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.
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.
MPO staff observed the following operating conditions in the field:
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.)
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.
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.
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.
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:
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 |
---|---|---|---|---|---|---|---|
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.
Short-Term Solution:
Medium-Term Solution:
SAA/saa
cc: M. Karas, MassDOT District 4
J. Onorato, MassDOT District 4 C. Raphael, MassDOT District 4 P. Nelson, MassDOT Planning
Figures
Appendixes
A. Turning Movement and Automatic Traffic Recorder Counts
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.