HomeMy WebLinkAboutTraffic Memo with Attachments 8 18 22
Engineers Scientists Planners Designers
101 Walnut Street, PO Box 9151, Watertown, Massachusetts 02471
P 617.924.1770 F 617.924.2286 www.vhb.com
\\gbldata\projects\Wat-TS\15578.00 Yarmouth Subdivision\docs\memos\Traffic Memo Update 8 22.docx
To: Town of Yarmouth Date: August 18, 2022
Project #: 15405.00
From: Randall Hart, Principal Re: Proposed Subdivision Traffic Assessment
Introduction
On behalf of the Davenport Companies, Vanasse Hangen Brustlin, Inc. (VHB) has prepared a transportation assessment
of the proposed Miracle Way subdivision located on Lot 2 Route 6A in Yarmouth, Massachusetts. The following
memo provides review of existing accident history along Route 6A at the proposed site driveway and adjacent
intersection, projections of traffic for the subdivision, and review of site distance for the proposed driveway and
adjacent roadway.
Crash Summary
A detailed crash analysis was conducted to identify potential vehicle accident trends and/or roadway deficiencies in
the immediate area of the proposed site driveway. The most current vehicle accident data for the traffic study area
intersections were obtained from MassDOT for the years 2015 to 2019. The MassDOT database is comprised of crash
data from the Massachusetts Registry of Motor Vehicles (RMV) Division primarily for use in traffic studies and safety
evaluations. Data files are provided for an entire city or town for an entire year, though it is possible that some crash
records may be omitted either due to individual crashes not being reported, or the city crash records not being
provided in a compatible format for RMV use.
Crash rates are calculated based on the number of accidents at an intersection and the volume of traffic traveling
through that intersection on a daily basis. Rates that exceed MassDOT’s average for accidents at intersections in the
MassDOT district in which the town or city is located could indicate safety or geometric issues for a particular
intersection. For our study area, the calculated crash rates for the study area intersections were compared to the
MassDOT District 5 (the MassDOT district for Yarmouth) average. The current MassDOT average crash rate for
unsignalized and signalized intersections in District 5 is 0.57 and 0.75 crashes per million entering vehicles,
respectively. In other words, on average, 0.57 crashes occurred per million vehicles entering unsignalized intersections
throughout District 5.
A summary of the study area intersections vehicle accident history based on the available RMV data is presented in
Table 1 and the detailed crash data is provided in the Attachments to this memorandum.
Town of Yarmouth Ref: 15578.00
August 11, 2022
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Table 1 Vehicular Crash Data (2015 - 2019)
Route 6A at Hockanom Road
Route 6A at Kencomsett Circle
Route 6A at Outward Reach
Signalized? No No No MassDOT Average Crash Rate 0.57 0.57 0.57
Year
2015 1 0 1 2016 1 0 1
2017 0 0 0
2018 0 0 0
2019 0 0 0
Total 2 0 2
Yearly Average 0.4 0.0 0.4
Collision Type
Angle 0 0 0
Head-on 0 0 0 Rear-end 1 0 2 Sideswipe, opposite direction 0 0 0
Sideswipe, same direction 0 0 0
Single Vehicle Crash 1 0 0
Not reported 0 0 0
Severity
Fatal Injury 0 0 0
Non-Fatal Injury 0 0 0
Property Damage Only 2 0 2
Not Reported 0 0 0
Time of day
Weekday ,7:00 AM - 9:00 AM 0 0 0
Weekday, 4:00 – 6:00 PM 1 0 1
Saturday 11:00 AM – 2:00 PM 0 0 1
Weekday, other time 0 0 0
Weekend, other time 1 0 0
Pavement Conditions
Dry 2 0 2
Wet 0 0 0
Snow 0 0 0
Sand, mud, dirt, oil, gravel 0 0 0
Not reported 0 0 0
Non-Motorist (Bike, Ped) 0 0 0
Source: Crash data was obtained from MassDOT Crash Portal, accessed December 27, 2021.
Engineers Scientists Planners Designers
101 Walnut Street, PO Box 9151, Watertown, Massachusetts 02471
P 617.924.1770 F 617.924.2286 www.vhb.com
\\gbldata\projects\Wat-TS\15578.00 Yarmouth Subdivision\docs\memos\Traffic Memo Update 8 22.docx
As shown in Table 3, there were two crashes at the intersection of Route 6A at Hockanom Road over the five-year
period between 2015 and 2019. It should be noted that one of the crashes reported involved a single vehicle colliding
with an animal on the roadway within the vicinity of this intersection. This crash therefore may have occurred
independently of the intersection geometry which should be considered when examining the crash data at this
location.
No reported crashes occurred at the intersection of Route 6A at Kencomsett Circle over the five-year period.
Highway Safety Improvement Program
In addition to calculating the crash rate, study area intersections should also be reviewed in the MassDOT’s Highway
Safety Improvement Program (HSIP) database. An HSIP-eligible cluster is one in which the total number of
“equivalent property damage only“1 crashes in the area is within the top 5% of all clusters in that region. Being HSIP-
eligible makes the location eligible for FHWA and MassDOT funds to address the identified safety issues at these
locations. As part of this effort, VHB reviewed this database and found that the intersections referenced above are not
HSIP locations.
Trip Generation
The rate at which any development generates traffic is dependent upon a number of factors such as size, location, and
concentration of surrounding developments. The site is currently vacant. The proposed development consists of a
14-lot single-family home residential subdivision. The proposed site plan is included in the Attachments.
Trip generation estimates for the proposed use were projected using trip generation rates published by the Institute
of Transportation Engineers (ITE) Trip Generation, 11th Edition2. The number of vehicle-trips generated by the
residential subdivision were estimated based on ITE LUC 210 (Single-Family Detached Housing). The estimated trip
generation for the proposed subdivision is presented below in Table 2.
1 “Equivalent property damage only” is a method of combining the number of crashes with the severity of the crashes based on a weighted scale. Crashes involving property damage only are reported at a minimal level of importance, while collisions involving personal injury (or fatalities) are weighted more heavily. 2 Trip Generation, 11th Edition, Institute of Transportation Engineers, Washington D.C., 2021.
Town of Yarmouth Ref: 15578.00
August 11, 2022
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Table 2 Trip Generation Summary
Site-Generated Trips a
Weekday Daily
Enter 83
Exit 83
Total 166
Weekday Morning Peak Hour
Enter 3
Exit 9
Total 12
Weekday Evening Peak Hour
Enter 10
Exit 6
Total 16
Saturday Daily
Enter 72
Exit 72
144
Saturday Midday Peak Hour
Enter 12
Exit 10
Total 22
a. Trip Generation estimate based ITE LUC 210 (Single-Family Detached Housing) for 14 units.
As shown in Table 2, the development is expected to generate approximately 12 trips (3 entering/ 9 exiting) during
the weekday morning peak hour, 16 trips (10 entering/ 6 exiting) during the evening peak hour, and 22 trips (12
entering/ 10 exiting) during the Saturday midday peak hour.
Sight Distance
Access to the site is proposed via a single access driveway (Miracle Way) to Route 6A. Alternative access was also
considered via the rear of the property to Eileen Street. Eileen Street intersects with Outward Reach Road which
provides access to Route 6A. Both roadways are residential in nature. If access were solely provided from Eileen
Street all site related traffic would be directed through existing residential streets. Under the proposed plan no access
to Eileen Street is proposed and all site traffic would be directly to Route 6A thereby avoiding the existing residential
neighborhood to the east.
Town of Yarmouth Ref: 15578.00
August 11, 2022
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VHB conducted a sight distance analysis, conforming to guidelines of the American Association of State Highway and
Transportation Officials (AASHTO)3, at Route 6A at Hockanom Road and Route 6A at the location of the proposed site
driveway. Sight distance is generally divided into two categories: Stopping Sight Distance (SSD) and Intersection Sight
Distance (ISD). Stopping Sight Distance (SSD) is the distance required for a vehicle approaching an intersection from
either direction to perceive, react and come to a complete stop before colliding with an object in the road, in this case
the exiting vehicle from a driveway. In this respect, SSD can be considered as the minimum visibility criterion for the
safe operation of an unsignalized intersection.
Intersection Sight Distance (ISD) is based on the time required for perception, reaction and completion of the desired
critical exiting maneuver once the driver on a minor street or driveway approach decided to execute the maneuver.
Calculation for the critical ISD includes the time to (1) turn left, and to clear the half of the intersection without
conflicting with the vehicles approaching from the left; and (2) accelerate to the operating speed of the roadway
without causing approaching vehicles to unduly reduce their speed. In this context, ISD can be considered as a
desirable visibility criterion for the safe operation of an unsignalized intersection. Essentially, while SSD is the
minimum distance needed to avoid collisions, ISD is the minimum distance needed so that mainline motorists will not
have to substantially reduce their speed due to turning vehicles. To maintain the safe operation of an unsignalized
intersection, ISD only needs to be equal to the stopping sight distance, though it is desirable to meet ISD
requirements by themselves.
To calculate the required SSD and ISD at the proposed unsignalized Site driveway intersections, a 45miles-per-hour
(mph) design speed was used based on the posted speed limit. Table 3 summarizes the sight distance analysis.
Table 3 Sight Distance Analysis Summary
Stopping Sight Distance (ft) a Intersection Sight Distance (ft) a
Traveling Required Measured Turning Desired Measured
Route 6A at Proposed Site
Driveway
Eastbound 360 750+ Left 500 750+
Westbound 360 750+ Right 430 730+
Route 6A at Hockanom Road Eastbound 360 840+ Left 500 395+
Westbound 360 410+ Right 430 900+
a Based on guidelines established in A Policy on the Geometric Design of Highways and Streets, Seventh Edition(2nd Printing), American Association of State Highway and Transportation Officials (AASHTO), 2018 for a posted speed limit 45-mph.
As shown in Table 3, the minimum stopping sight distance (SSD) and intersection sight distance at the proposed site
driveway assuming that necessary clearing along the site frontage is conducted. A sight line diagram is provided in
the attachments showing the area to cleared.
3 A Policy on the Geometric Design of Highways and Streets, American Association of State Highway and Transportation Officials, 2011.
Town of Yarmouth Ref: 15578.00
August 11, 2022
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Attachments
Attachments
Route 6A at Hockanom RoadCrash Number City Town Name Crash Date Crash Severity Crash Time Max Injury Severity Reported Number of Vehicles Police Agency TypeAge of Driver ‐ Youngest Known Age of Driver ‐ Oldest KnownDriver Contributing Circumstances (All Drivers) Light Conditions Manner of Collision MassDOT DistrictNon‐Motorist Type (All Persons) RMV Document Numbers Road Surface Condition Total Fatalities Total Non‐Fatal InjuriesVehicle Actions Prior to Crash (All Vehicles)Vehicle Configuration (All Vehicles)Vehicle Travel Directions (All Vehicles) Weather Conditions Crash Report IDsMost Harmful Event (All Vehicles) Street Number Roadway Near Intersection Roadway4083564 YARMOUTH 07/28/2015Property damage only (none injured) 5:13 PM No injury 2 Local police 25‐34 65‐74D1: (Inattention) / D2: (No improper driving) Daylight Rear‐end 5 PW201525700141 Dry 0 0V1: Travelling straight ahead / V2: Slowing or stopped in trafficV1:(Passenger car) / V2:(Passenger car) V1: E / V2: E Clear 15‐321‐ACV1:(Collision with motor vehicle in traffic) / V2:(Collision with motor vehicle in traffic) 644 ROUTE 6A Rte 6A E HOCKANOM ROAD4139515 YARMOUTH 01/23/2016Property damage only (none injured) 8:16 AM No injury 1 Local police 55‐64 55‐64 D1: (No improper driving) Daylight Single vehicle crash 5 PW201602500196 Dry 0 0 V1: Travelling straight ahead V1:(Passenger car) V1: E Cloudy 16‐24‐ACV1:(Collision with animal ‐ deer) HOCKANOM RD / ROUTE 6AData Level: CRASHQuery Type: SpatialCriteria: If you conducted an Advanced Query your SQL statement will be listed here
ITE TRIP GENERATION WORKSHEET
(11th Edition, Updated 2021)
LANDUSE:Single-Family Detached Housing
LANDUSE CODE:210 Independent Variable --- Number of Units
SETTING/LOCATION:General Urban / Suburban
JOB NAME:14 units
JOB NUMBER:
RATES:Total Trip Ends Independent Variable Range
# Studies R^2 Average Low High Average Low High Enter Exit
DAILY 174 0.95 9.43 4.45 22.61 246 10 2,945 50% 50%
AM PEAK (ADJACENT ST) 192 0.90 0.70 0.27 2.27 226 10 2,945 26% 74%
PM PEAK (ADJACENT ST) 208 0.92 0.94 0.35 2.98 248 10 2,945 63% 37%
TRIPS:BY AVERAGE BY REGRESSION
Total Enter Exit Total Enter Exit
DAILY 134 67 67 166 83 83
AM PEAK (ADJACENT ST)10 3 7 12 3 9
PM PEAK (ADJACENT ST)13 8 5 15 10 6
RATES:Total Trip Ends Independent Variable Range
# Studies R^2 Average Low High Average Low High Enter Exit
DAILY 63 0.91 9.48 3.36 16.52 179 15 1,000 50% 50%
PEAK OF GENERATOR 42 0.89 0.92 0.41 1.78 152 15 644 54% 46%
TRIPS:BY AVERAGE BY REGRESSION
Total Enter Exit Total Enter Exit
DAILY 134 67 67 144 72 72
PEAK OF GENERATOR 13 7 6 22 12 10
RATES:Total Trip Ends Independent Variable Range
# Studies R^2 Average Low High Average Low High Enter Exit
DAILY 60 0.94 8.48 2.61 16.44 186 15 1,000 50% 50%
PEAK OF GENERATOR 40 0.92 0.83 0.36 1.67 163 15 644 53% 47%
TRIPS:BY AVERAGE BY REGRESSION
Total Enter Exit Total Enter Exit
DAILY 120 60 60 54 27 27
PEAK OF GENERATOR 12 6 5 16 8 8
Directional
Distribution
Directional
Distribution
Directional
Distribution
WEEKDAY
SATURDAY
SUNDAY
Stopping Sight Distance and Intersection Sight Distance Calculator [v0.97]
Based on 'A Policy on Geometric Design of Highways and Streets', AASHTO, 2004
Section I Section III
Project Information ISD and SSD Calculations (rounded up to the next highest 5 feet) [sources: SSD - AASHTO, pp.110-117; ISD - AASHTO, pp. 650 - 664]
Project Number: 15578.00 Analyst: VHB Cases are described in detail on subsequent pages. In summary…
City/Town, State: Yarmouth, MA B1: left turn from minor road, from stop control
Location: Route 6A at Site Driveway Client: B2: right turn from minor road, from stop control
B3: crossing maneuver from minor road, from stop control, assuming left- and right turns
Street Names and Directions Street Notes are not permitted [otherwise, case B1 or B2 would supercede]
Major Street name: Route 6A
Minor Street name: Site Driveway NB/SB Desirable Calculated… Condition Met?
Minor Street intersects from the: … ISD, case B1: 500 Yes
… ISD, case B2: 430 Yes
The minor street predominantly serves…… ISD, case B3: 430 Yes
Sight distance location intersection is…[note: if number of lanes crossed exceeds 6, or if grades are steep, consult the manual]
Total number of lanes on Major Street is…
Grade Information [enter down slope as a negative number]Minimum Calculated …Condition Met?
Major Street Approach Grade: 0.00%EB … ISD, case B1: 360 Yes
0.00%WB … ISD, case B2: 360 Yes
Minor Street Approach Grade: 0.00%SB … ISD, case B3: 360 Yes
0.00%NB [note: minimum ISD is equal to required SSD]
Major Street Speed Information
Posted Observed *Calculated …Condition Met?
45 EB 45 … SSD: 360 traveling EB Yes
45 WB 45 360 traveling WB Yes
* note: off-peak 85th percentile speeds
Section II Section IV
ISD and SSD Observations AASHTO Guidance
Instructions on how to observe and measure ISD and SSD are included on subsequent pages.Refer to AASHTO for specific guidance on SSD and ISD if presented with an unusual/atypical case.
Adequate ISD is not needed at signalized intersections, assuming traffic signal heads are visible on all approaches.
Any object that would obstruct the driver's view should be removed or lowered, if practical. Such objects include buildings,
parked cars, highway structures, hedges/vegetation/trees/bushes/unmowed lawn, walls, fences, and terrain.
For ISD, an object should be considered an obstruction if it obstructs the vision of a driver whose eye height is 3.5 feet above the
roadway surface and the object to be seen is 3.5 feet above the surface of the intersecting road.
Where horizontal sight restrictions occur on downgrades, particularly at the ends of long downgrades, it is desirable to provide
SSD that exceeds those values indicated above (refer to page 114 of AASHTO).
Limiting Factors:
Observed ISD: 750 looking left [west]
(rounded to nearest 5 feet)730 looking right [east]
Observed SSD: 750 traveling EB
(rounded to nearest 5 feet)750 traveling WB
SSD - Stopping sight distance is the distance required for a vehicle approaching an intersection from either direction to perceive,
react, and come to a complete stop before colliding with the exiting vehicle from a driveway. In this respect, SSD can be
considered as the minimum visibility criterion for the safe operation of an unsignalized intersection.
ISD - Intersection sight distance is the distance that is based on the time required for perception, reaction and completion of the
desired critical exiting maneuver [typically, a left turn] once the driver on a minor street approach [or a site drive] decides to
execute the maneuver. Calculation for the critical ISD includes the time to [1] turn left, and to clear the near half of the
intersection without conflicting with the vehicles approaching from the left; and [2] upon turning left, to accelerate to the
operating speed on the roadway without causing approaching vehicles on the main road to unduly reduce their speed. In this
context, ISD can be considered as a desirable visibility criterion for the safe operation of an unsignalized intersection.
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