ROAD SAFETY AUDIT
Granite Avenue at Squantum Street
MassDOT Project #607754
Town of Milton
June 17, 2015
Prepared For:
MassDOT Highway Division
Prepared By:
Nitsch Engineering
2 Center Plaza, Suite 430
Boston, MA 02108
Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Table of Contents
Project Data ................................................................................................................................. 1
Background ................................................................................................................................. 2
Project Location and Description .............................................................................................. 2
Audit Observations ..................................................................................................................... 6
Potential Safety Enhancements ............................................................................................... 13
Summary of Road Safety Audit ............................................................................................... 14
List of Tables
Table 1. Participating Audit Team Members ........................................................................................ 1
Table 2. Time Frame and Costs Breakdown ....................................................................................... 14
Table 3. Potential Safety Enhancement Summary – Granite Avenue at Squantum Street ............ 15
List of Figures
Figure 1: Locus Map ............................................................................................................................... 4
Figure 2: Study Location ........................................................................................................................ 5
List of Appendices
Appendix A: RSA Meeting Agenda
Appendix B: RSA Audit Team Contact List
Appendix C: Detailed Crash Data
Appendix D: Traffic Counts
Appendix E: Road Safety Audit References
Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Project Data
A Road Safety Audit for the intersection of Granite Avenue at Squantum Street occurred on Wednesday,
June 3, 2015 in Milton, MA. As indicated in Table 1, the audit team consisted of representatives from the
Town of Milton, MassDOT Traffic Engineering & Safety, MassDOT District 6, and Central
Transportation Planning Staff (CTPS). The group observed operations and safety at the study intersection
and this report documents the audit team’s findings. The RSA agenda can be found in Appendix A.
Contact information for the team members can be found in Appendix B.
Table 1. Participating Audit Team Members
Name
Steve Farr
Jeff Bandini
John Thompson
Courtney Dwyer
Kevin Chiang
Amitai Lipton
Kevin Foley
Dale Horsman
Mark Alba
Annemarie Fagan
William Clark
Joseph Lynch
John Calabro
Chen-Yuan Wang
Agency/Affiliation
Nitsch Engineering
Nitsch Engineering
Town of Milton – Engineering Department
MassDOT District 6
MassDOT Boston Traffic Operations
MassDOT District 6 Traffic
Milton Police Department
Town of Milton – Engineering Department
Milton Police Department
Town Administrator
Town Planning Director
Town of Milton – DPW - Director
Town of Milton – DPW - Wire
Boston Region MPO/CTPS
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Background
The Road Safety Audit (RSA) is one of the first steps in this design process as well as a necessary step for
the project to be eligible to receive Highway Safety Improvement Program (HSIP) federal funds for
construction. The goal of this RSA is to identify potential safety issues that can be addressed with shortterm improvements prior to construction and long-term improvements that can be incorporated into
design. All improvements should adhere to the MassDOT guidelines for roadway and intersection
design.
The RSA is a collaborative process by state, municipal, law enforcement, public works, and design
consultants. The process involves conducting a meeting to discuss current crash data and safety issues at
the site, visiting the site to discuss possible solutions that would improve safety, and preparing a written
report that outlines the safety issues discussed along with the costs, timeline, and agency responsibility for
implementing improvements.
Project Location and Description
The Locus Map of the study area is shown in Figure 1. An aerial map of the study location of Granite
Avenue at Squantum Street is shown in Figure 2.
Granite Avenue is classified as an urban minor arterial that runs in a north-south direction through the
project area, with its northern terminus at Gallivan Boulevard in the City of Boston and its southern
terminus at Interstate 93 at Interchange #9 in the Town of Milton.
Squantum Street is classified as an urban minor arterial that runs in an east-west direction through the
project area, with its western terminus just west of the Interstate 93 underpass and its eastern terminus at
Clement Terrace, where it continues as West Squantum Street and East Squantum Street east of Hancock
Street (Route 3A) in the City of Quincy.
Granite Avenue north and west of Squantum Street, Squantum Street east of Granite Avenue to the
intersection of Antwerp Street, and the intersection of Granite Avenue at Squantum Street itself, is
maintained by the Massachusetts Department of Transportation (MassDOT). Granite Avenue south of
Squantum Street, and Squantum Street east of Antwerp Street, is maintained by the Town of Milton.
Granite Avenue serves approximately 20,000 vehicles per day and Squantum Street serves approximately
14,000 vehicles per day east of the intersection and 12,000 vehicles per day west of the intersection. The
posted speed limit on Granite Avenue, north of Squantum Street is 45 miles per hour (mph). There is no
posted speed limit south on Granite Avenue south of Squantum Street. The posted speed limit on
Squantum Street, east of Granite Avenue is 30 miles per hour (mph). There is no posted speed limit on
Squantum Street west of Granite Avenue.
Nitsch Engineering evaluated the last three years of available crash data (2010 – 2012) from MassDOT to
establish some of the existing safety concerns at the intersection. Of the crash data researched for the
three-year period, 19 total crashes were documented, most of which were angle crashes involving the
collision of vehicles traveling from Granite Avenue northbound and Squantum Street westbound. The
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
crash rate, the quantity of crashes at the intersection per Million Entering Vehicles (MEV) for the three
year 2010-2012 period was 0.49 per MEV. This is below the signalized intersection average for
Statewide (0.80 per MEV) and District 6 (0.76 per MEV)1.
Audit participants noted that there have been many changes at and near the intersection since the 20102012 period that may have had an effect on crash quantity, type, and severity. These changes include
construction activity, detours from the nearby Neponset River Bridge Project, utility work, resurfacing,
and restriping.
As a result, subsequent to the Road Safety Audit, Nitsch Engineering obtained crash information from the
Town of Milton for crash years 2013 and 2014. Of the crash data researched for the two-year period, four
crashes were documented, three of which were of angle type. The crash rate for the two-year period
2013-2014 was 0.15, which represents approximately a 70% reduction from the three-year period from
2010-2012. Appendix C includes the crash data at this location.
1
2010 Average Crash Rates, per Million Entering Vehicles by Intersection Type, MassDOT, Highway Division
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Figure 1: Locus Map
Road Safety Audit
Granite Avenue at Squantum Street
Milton, MA
Data Source: MassGIS
Nitsch Project #9720.4
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Figure 2: Study Location
Road Safety Audit
Granite Avenue at Squantum Street
Milton, MA
Data Source: MassGIS
Nitsch Project #9720.4
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Audit Observations
Based on a summary of the existing crash information and traffic operations, audit participants identified
the following safety issues:

Intersection Geometry:
o
o
The northwest and southeast corners of the intersection contain large radii, which
contributes to the following:

Motorists executing the southbound right-turn and northbound right-turn
movements at relatively high rates of speed,

Low pedestrian sight-distance

Relatively large interior area of the intersection, necessitating long vehicle
clearance timing and long pedestrian phase timing.
The median islands on the Squantum Street eastbound and westbound approach extend
past the crosswalk markings and into the intersection and no level-cut through is provided
for pedestrians.
There are no pedestrian ramps at the intersection and the center islands on
both Squantum Street approaches block the pedestrian travel path.
o
The distance and turning radius necessary to successfully navigate the left-turn
movements from Squantum Street westbound onto Granite Avenue southbound and from
Squantum Street eastbound onto Granite Avenue northbound is difficult without dashed
white or dashed yellow lane lines present within the intersection.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4

o
The Squantum Street westbound approach prevents vehicles from forming multiple lanes
when multiple vehicles are queued.
o
The Squantum Street westbound approach contains two lanes – a shared left-turn/through
lane, and an unmarked lane. Given this configuration, vehicles can travel as a through
movement from both lanes, however, Squantum Street west of the intersection does not
contain two receiving lanes.
o
The Squantum Street eastbound approach contains two lanes that are unmarked - a shared
left-turn/through lane, and an unmarked lane. Given this configuration, vehicles can
travel as a through movement from both lanes, however, Squantum Street west of the
intersection does not contain two receiving lanes.
o
The Squantum Street eastbound approach contains two general purpose lanes with no
indication of the lane assignments. Audit participants noted that the left-most lane
functions as both a left-turn and a through lane and the right-most lane functions as a leftturn, through, and right-turn lane. This can cause confusion when motorists execute a
through movement from the left-most lane while simultaneously, another motorist
executes a left-turn lane from the right-most lane. Furthermore, vehicles can travel as a
through movement from both lanes, however, Squantum Street east of the intersection
does not contain two receiving lanes.
Traffic Operations:
o
According to audit participants, Squantum Street westbound approaching the intersection
has undergone a few recent modifications to the lane configuration different than
indicated in Figure 2. The current configuration contains two approach lanes, the leftmost lane permitting a shared left-turn/through movement, noted by pavement marking
arrows, and the right-most lane showing no indication, but functions as a shared
through/right-turn lane. Pavement markings are not present for the right-most lane and
advanced warning of the lane configuration is not present. This is further exacerbated
due to the vertical and horizontal curves approaching the intersection, which may cause
motorists to execute last-minute lane changes.
o
Both Squantum Street eastbound and westbound approaches lack traffic signal arrow
indications that depict that the movements are protected during their respective phases.
This can cause driver hesitation through the intersection, which may lead to rear-end
collisions, as was indicated in at least one crash report.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Looking eastbound on Squantum Street. No lane assignment pavement
markings or signage. Traffic signals lack arrow indications that depict
that vehicle phase is protected. Departing the intersection eastbound, only
one receiving lane is present.
o
South of the intersection, Granite Avenue northbound contains three approach lanes – a
shared left-turn/through lane, a through-only lane, and a right-turn only lane. The lanes
are not collinear through the intersection and auxiliary markings are present to guide
motorists through the intersection.
o
North of the intersection, Granite Avenue southbound contains two travel lanes.
Approaching the intersection, the right-most lane becomes a right-turn only lane, which
contains an overlap phase that allows a free right-turn during the Squantum Street
eastbound phase. No advanced warning is given regarding the lane configuration,
causing some motorists in the right-lane desiring to travel through the intersection to
merge into the left-most lane just prior to the intersection, or remain in the right-turn only
lane to travel through, thereby blocking the progression of right-turns. Vehicles traveling
in the left-most lane that desire to travel through may observe a vehicle ahead that is
desiring to turn left. In an attempt to not pass the left-turning vehicle, the through vehicle
may merge into the right-turn only lane to travel through the intersection. This is
exacerbated by the crest vertical curve approaching the intersection. Additionally, the
left-turns from Granite Avenue onto Squantum Street are permissive only.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Looking southbound on Granite Avenue. Right-most lane becomes a
right-turn only lane with a right-turn overlap phase during the
Squantum Street eastbound phase.
o
The intersection is not currently coordinated with the intersections located at East Milton
Square, located approximately 0.20 miles south of the intersection. The East Milton
Square intersection is currently being re-designed by MassDOT and coordination with
the project intersection may aid progression through the corridor, relieve vehicle
congestion, and minimize driver frustration.
o
Granite Avenue northbound is frequently used as an Interstate 93 by-pass during the
weekday morning peak hours, particularly when there is a traffic incident reported on
Interstate 93. Traffic volumes indicate a large fluctuation in vehicles between the
Wednesday and Thursday that data was collected, indicating an incident may have been
present on Thursday. This may contribute to drivers becoming more aggressive along
the roadway.
o
A non-standard “No Turn on Red” sign is mounted on the mast arm support located on
the northwest corner of the intersection, indicating the restriction for the Squantum Street
westbound approach.
o
The ‘Keep Right’ signs located throughout the intersection are mounted too low,
approximately 4 feet above grade, and contribute to blocked driver sight distance.
o
Signage on the Granite Avenue northbound approach are non-standard. Two signs, a
“Blind Driveway” and “No Turn on Red”, are mounted too low to the ground on the mast
arm post located in the southeast corner of the intersection, causing a potential hazard to
pedestrians. A directional sign to North Quincy and a sign for Good Shepherd Lutheran
Church are mounted on a double-sign post at the approach and are damaged.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Signage is mounted too low, causing a potential hazard to pedestrians.
o
The intersection was recently re-striped, but did not extend far to the south along Granite
Avenue, which may cause difficulty in vehicle positioning approaching the intersection
from northbound Granite Avenue approach.
o
Two signs were noted as knocked-down or missing, the bus stop sign on the southwest
corner of the intersection and a ‘keep right’ sign on the island at the Squantum Street
westbound approach.
Visibility:
o
The Granite Avenue northbound and southbound approaches do not contain supplemental
post-mounted signals to compliment the signals mounted on the mast arms.
o
Audit participants discussed possible reasons for the unusually high percentage of angle
crashes between northbound Granite Avenue vehicles and westbound Squantum Street
vehicles. These approaches are controlled by separate signal phases and do not conflict.
Crash reports indicate that six of the eight angle crashes were ‘red-light running’
incidents. A tree in the southeast corner of the intersection blocks the visibility of the
mast-arm mounted “doghouse” signal head at the northbound Granite Avenue approach.
None of the traffic signals for any direction contain backplates, which can provide proper
signal backdrop to enhance visibility for motorists.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Tree limbs blocking signal indication. Note no backplates on signals .

Accessibility:
o
Pedestrian signals are present at the intersection, however, several signal heads are not
illuminated. Additionally, several of the signal heads do not meet the current standards,
as they contain scripted text and not the current ‘raised hand’ and ‘walking person’
indications.
Pedestrian signal head at the northeast corner is not illuminated and
is non-standard
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
o
Pedestrian ramps are not present at the intersection or at the crosswalk termini.
Furthermore, the crosswalk extends through the median islands at the two Squantum
Street approaches, and there are no pedestrian ramps within the median.
o
There are bus stops at the northeast and southwest corners of the intersection. The
locations of the bus stops may be problematic for vehicles turning from both Squantum
Street approaches onto Granite Avenue.

Bicycle Accommodation: Bicycle accommodations are not present at the intersection with the
exception of Granite Avenue southbound, south of the intersection where a wide shoulder is
present.

Emergency Vehicle Pre-emption: The intersection does not have an emergency vehicle preemption system.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Potential Safety Enhancements
Following review of crash data and traffic counts and a discussion of potential safety issues, audit
participants recommend the following.









Decrease the radii of the northwest and southeast corners of the intersection. Realign and restripe
the intersection to decrease the interior area of the intersection, which may decrease vehicle travel
speeds, increase sight distance for oncoming traffic to the crosswalk approaches, provide more
space to install pedestrian ramps, and would allow for shorter vehicle and pedestrian clearance
intervals.
Decrease the length and possibly the width of the median islands of the Squantum Street
eastbound and westbound approaches.
Investigate adding turning lane guide markings within the intersection for Squantum Street
westbound and eastbound.
Examine the feasibility of an exclusive left-turn lane and/or a protected phase for Granite Avenue
southbound.
Add signage, restripe, and possibly widen the Granite Avenue southbound approach such that the
vehicles in the right-most lane do not unintentionally end up in the right-turn only lane.
Add traffic signal arrow indications for the Squantum Street eastbound and westbound
approaches to depict the separate protected phases.
Investigate adding pavement markings and signage to indicate ideal lane configuration for
Squantum Street eastbound. Based on audit observations, the left-lane would function as a ‘leftturn only’ lane and the right-lane would function as a shared left-turn, through, and right-turn
lane. This should be studied in further detail before being implemented.
Add pavement markings and signage to indicate configuration for Squantum Street westbound
and note the disposition of the far-right lane.
Modify the edge of pavement and align striping of the Granite Avenue northbound approach such
that the travel lanes through the intersection are collinear.

Mount the “Blind Driveway” and “No Right Turn” signs at the correct height such that they are
visible and do not present a hazard to pedestrians. Furthermore, all signage at the intersection
should be installed by, or with the permission, of MassDOT.

Establish an underground conduit connection such that the intersection is coordinated with the
East Milton Square intersection improvement project. While this is an operational improvement,
it would provide continuity between the two locations and would potentially limit delays and
driver frustration.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4




Continue the striping of the Granite Avenue northbound approach further south towards East
Milton Square.
Refurnish the signage for the bus stop on the southwest corner and the ‘keep right’ sign for the
median approaching the intersection via Squantum Street westbound.
Trim vegetation on the southeast corner such that the signals mounted on the mast arm for the
Granite Avenue northbound are visible.
Mount supplemental post-mounted traffic signals for the Granite Avenue northbound and
southbound approaches.

Construct pedestrian ramps at the intersection and the crosswalk termini.

Furnish new pedestrian signals that include the ‘raised hand’ and ‘walking person’ indications.

Incorporate bicycle accommodation at each intersection approach.

Install emergency vehicle pre-emption system.
Summary of Road Safety Audit
MassDOT has retained Nitsch Engineering to prepare this Road Safety Audit (RSA) for the intersection
of Granite Avenue at Squantum Street. As part of the RSA process going forward, each of the potential
safety enhancements is classified by time frame and cost, as shown in Table 2.
Table 2. Time Frame and Costs Breakdown
Time Frame
Short-term
< 1 year
Mid-term
1-3 years
Long-term
> 3 years
Low
Medium
High
Costs
< $10,000
$10,000-$50,000
> $50,000
The safety issues, potential improvements, estimated safety payoff, time frame, and cost for the
intersection of Granite Avenue at Squantum Street are summarized in Table 3.
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Table 3. Potential Safety Enhancement Summary – Granite Avenue at Squantum Street
Safety Issue
Intersection
Geometry
Safety Enhancement
Reconstruct intersection to decrease the radii of the corners of
the intersection, install new pedestrian ramps, provide bicycle
accommodation, and any other necessary updates to conform to
latest MassDOT standards.
Decrease the length and width of the median islands of the
Squantum Street eastbound and westbound approaches to
provide adequate approach width and provide a clear path for
pedestrians.
As part of the reconstruction of the intersection, furnish new traffic
signal system to include new mast arms, posts, signals, conduit,
emergency vehicle pre-emption system, and any other necessary
equipment. Perform study to possibly reallocate traffic signal
phasing and timing, while incorporating possible reductions in
vehicle and pedestrian clearance intervals based on the new
intersection geometry.
Examine the feasibility of an exclusive left-turn lane and/or
protected phase for Granite Avenue southbound.
Traffic Operations
Widen the Granite Avenue southbound approach to the west side
of the intersection to better align the southbound approach
through the intersection.
Add signage and restripe the Granite Avenue southbound
approach such that the vehicles in the right-most lane
approaching the intersection do not unintentionally end up in the
right-turn only lane, and aide in vehicles using the right-turn lane
as a de-facto through lane when left-turning vehicles are queued
in the left-lane
Add pavement markings and signage to indicate ideal lane
configuration for Squantum Street eastbound. Based on audit
observations, the left-lane would function as a ‘left-turn only’ lane
and the right-lane would function as a shared left-turn, through,
and right-turn lane. A study may be warranted to confirm the
observations.
Safety
Payoff
Time
Frame
Cost
Responsible
Agency
High
Long-term
High
MassDOT
High
Short-term
Medium
MassDOT
High
Long-term
High
MassDOT
High
Mid-term
Medium
MassDOT
Medium
Mid-term
Medium
MassDOT/Town
of Milton
Medium
Short-term
Low
MassDOT
High
Short-term
Low
MassDOT
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Road Safety Audit—Granite Avenue at Squantum Street, Milton
Nitsch Engineering 9720.4
Table 3: Potential Safety Enhancement Summary – Granite Avenue at Squantum Street (continued)
Safety Issue
Traffic Operations
(continued)
Visibility
Pedestrian & Bicycle
Accessibility
Emergency
Safety Enhancement
Re-mount the “Blind Driveway” and “No Right Turn” signs at the
correct height such that they are visible and do not present a
hazard to pedestrians. Furnish proper “No Turn on Red” signage
for Squantum Street westbound approach.
Establish an underground conduit connection such that the
intersection is coordinated with the East Milton Square
intersection improvement project, and provide striping continuity
between the two locations.
Refurnish the signage for the bus stop on the southwest corner
and the ‘keep right’ sign for the median approaching the
intersection via Squantum Street westbound. Mount all ‘keep
right’ signage at proper height.
Trim vegetation on the southeast corner such that the signals
mounted on the mast arm for the Granite Avenue northbound are
visible.
Construct pedestrian ramps at the intersection and the crosswalk
termini.
Furnish new pedestrian signals that include the ‘raised hand’ and
‘walking person’ indications.
Install emergency vehicle pre-emption system.
Safety
Payoff
Time
Frame
Cost
Responsible
Agency
Medium
Short-term
Low
MassDOT/Town
of Milton
Low
Long-term
Medium
MassDOT/Town
of Milton
Low
Short-term
Low
MassDOT/Town
of Milton
Medium
Short-term
Low
MassDOT/Town
of Milton
High
Mid-term
Medium
MassDOT
Medium
Short-term
Medium
MassDOT
High
Mid-term
High
MassDOT
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