HomeMy WebLinkAboutTraffic Memorandum with Attachments 10 11 23Engineers Scientists Planners Designers
101 Walnut Street, PO Box 9151, Watertown, Massachusetts 02471
P 617.924.1770 F 617.924.2286 www.vhb.com
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To: Town of Barnstable Date: October 11, 2023
Project #: 15934.00
From: Randall Hart, Principal Re: Proposed Residential Traffic Assessment
Introduction
On behalf of the Proponent, Vanasse Hangen Brustlin, Inc. (VHB) has prepared a transportation assessment of the
proposed 14-unit residential development to be located at 900 Old Stage Road in Barnstable, Massachusetts. The
following memo provides review of existing accident history along Old Stage Road near the proposed site driveway
and adjacent intersection, projections of traffic for the residential development proposed, and review of site distance
at the proposed driveway.
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 in the vicinity of the proposed
site driveway were obtained from MassDOT for the years 2015 to 2020. 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 Brewster) 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.
Based on a review of the MassDOT database, no crashes were identified at the nearby intersection of Antico Lane or in
the vicinity of the proposed site driveway along Old Stage Road for the most recent five years of data that is available.
Town of Barnstable Ref: 15934.00
October 11, 2023
Page 2
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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 no HSIP clusters existing in the immediate
vicinity of the site.
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 residential development
consists of four buildings totaling 14 residential units.
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 220 (Multi-Family Housing Low-Rise). The estimated trip
generation for the proposed subdivision is presented below in Table 1.
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 Barnstable Ref: 15934.00
October 11, 2023
Page 3
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Table 1 Trip Generation Summary
Residential Vehicle Trips
a
Weekday Morning Peak Hour
Enter 1
Exit 5
Total 6
Weekday Evening Peak Hour
Enter 4
Exit 3
Total 7
Saturday Midday Peak Hour
Enter 3
Exit 3
Total 6
a.Trip Generation estimate based ITE LUC 220(Multi-Family Housing Low rise) for 14 units.
As shown in Table 1, the development is expected to generate approximately 6 trips (1 entering/ 5 exiting) during the
weekday morning peak hour, 7 trips (4 entering/ 3 exiting) during the evening peak hour, and 6 trips (3 entering/ 3
exiting) during the Saturday midday peak hour.
Town of Barnstable Ref: 15934.00
October 11, 2023
Page 4
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Sight Distance
Access to the site is proposed via a single access driveway off Old Stage Road.
VHB conducted a sight distance analysis, conforming to guidelines of the American Association of State Highway and
Transportation Officials (AASHTO)3, at the location of the proposed site driveway at Old Stage Road. 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, the posted speed limit
of 35 miles-per-hour (mph) was used. Table 2 summarizes the sight distance analysis.
Table 2 Sight Distance Analysis Summary
Stopping Sight Distance (ft) a Intersection Sight Distance (ft) a
Traveling Required Measured Turning Desired Measured
Site Driveway at Old Stage Road Northbound 250 >500+ Looking Left 390 >500+
Southbound 250 >750+ Looking Right 335 700+
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), posted speed limit 35 mph
As shown in Table 2, the minimum stopping sight distance (SSD) and intersection sight distance (ISD) exceeds the
minimum requirements. Based on a field inspection there is currently some vegetation and overhanging trees that
have influence on the sight distance looking both north and south. With that in mind, we suggest the area be
trimmed back including the overhanging tree canopies and any ground growth in the site triangles. Pictures of this
condition are provided as an attachment to this document.
3 A Policy on the Geometric Design of Highways and Streets, American Association of State Highway and Transportation Officials, 2011.
Town of Barnstable Ref: 15934.00
October 11, 2023
Page 5
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Attachments
•Site Plan
•Trip Generation Worksheet
•Driveway Sight Line Pictures
•Sight Distance Worksheet
BAXTER NYE
ENGINEERING &
SURVEYING
Bayridge Realty, LLC
76 Tupper Road, Unit #10
Sandwich, MA 02563
Proposed Housing
900 Old Stage Road
Centerville, MA 02632
FOR PERMIT ONLY - NOT FOR CONSTRUCTION
SHEET TITLE
DATE:
CHECKED BY:
JOB NO:
DRAWN BY:
DESCRIPTIONDATE
PREPARED FOR:
PROJECT TITLE
SHEET NO
SCALE:
STAMP
CONSULTANT
FILE:
CONSULTANT
STAMP
COPYRIGHT c 2022, BY SMART ENGINEERING LLC, dba BAXTER NYE ENGINEERING & SURVEYING, ALL RIGHTS RESERVED. REPRODUCTION IN ANY FORM WITHOUT THE EXPRESS WRITTEN CONSENT OF THE COPYRIGHT HOLDER IS PROHIBITED
C3.3
Sight DIstance Plan
O:\2021\2021-040\CIVIL\PLOT\2021-040 SIGHT.dwg, 8/29/2023 12:36:05 PM, jlavelle, DWG To PDF.pc3, ARCH expand D (36.00 x 24.00 Inches), 1:1
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: 16163.00 Analyst: VHB Cases are described in detail on subsequent pages. In summary…
City/Town, State: Hyannis, Massachusetts B1: left turn from minor road, from stop control
Location: 900 Old Stage Road 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: Old Stage Road
Minor Street name: Site Driveway EB/WB Desirable Calculated… Condition Met?
Minor Street intersects from the: … ISD, case B1: 390 Yes
… ISD, case B2: 335 Yes
The minor street predominantly serves…… ISD, case B3: 335 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%NB … ISD, case B1: 250 Yes
0.00%SB … ISD, case B2: 250 Yes
Minor Street Approach Grade: 0.00%SB … ISD, case B3: 250 Yes
0.00%NB [note: minimum ISD is equal to required SSD]
Major Street Speed Information
Posted Observed *Calculated …Condition Met?
35 NB 35 … SSD: 250 traveling NB Yes
35 SB 35 250 traveling SB 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: 500 looking left [south]
(rounded to nearest 5 feet)700 looking right [north]
Observed SSD: 500 traveling NB
(rounded to nearest 5 feet)750 traveling SB
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.
\\vhb\gbl\proj\Wat-TE\16163.00 Bayridge Res Development\docs\memos\AASHTO_sight_distance_900 OSR last revised: 2006.08.01
ITE TRIP GENERATION WORKSHEET
(11th Edition, Updated 2021)
LANDUSE:Multi-Family Housing (Low-Rise): 2-3 Story - Not Close to Rail Transit
LANDUSE CODE:220 Independent Variable --- Number of Dwelling Units
SETTING/LOCATION:General Urban/Suburban
JOB NAME:14 dwelling units
JOB NUMBER:
RATES:Total Trip Ends Independent Variable Range
# Studies R^2 Average Low High Average Low High Enter Exit
DAILY 22 0.86 6.74 2.46 12.50 229 33 494 50%50%
AM PEAK OF GENERATOR 40 0.76 0.47 0.25 0.98 234 12 1,103 24%76%
PM PEAK OF GENERATOR 38 0.80 0.57 0.25 1.26 231 12 1,103 62%38%
AM PEAK (ADJACENT ST)49 0.79 0.40 0.13 0.73 249 12 1,103 24%76%
PM PEAK (ADJACENT ST)59 0.84 0.51 0.08 1.04 241 12 1,103 63%37%
TRIPS:BY AVERAGE BY REGRESSION
Total Enter Exit Total Enter Exit
DAILY 96 48 48 166 83 83
AM PEAK OF GENERATOR 7 2 5 33 8 25
PM PEAK OF GENERATOR 8 5 3 41 25 15
AM PEAK (ADJACENT ST)6 1 4 27 7 21
PM PEAK (ADJACENT ST)7 4 3 28 18 10
RATES:Total Trip Ends Independent Variable Range
# Studies R^2 Average Low High Average Low High Enter Exit
DAILY 1 --4.55 4.55 4.55 282 282 282 50%50%
PEAK OF GENERATOR 1 --0.41 0.41 0.41 282 282 282 51%49%
TRIPS:BY AVERAGE BY REGRESSION
Total Enter Exit Total Enter Exit
DAILY 64 32 32 ------
PEAK OF GENERATOR 6 3 3 ------
RATES:Total Trip Ends Independent Variable Range
# Studies R^2 Average Low High Average Low High Enter Exit
DAILY 1 --3.86 3.86 3.86 282 282 282 50%50%
PEAK OF GENERATOR 1 --0.36 0.36 0.36 282 282 282 55%45%
TRIPS:BY AVERAGE BY REGRESSION
Total Enter Exit Total Enter Exit
DAILY 56 28 28 ------
PEAK OF GENERATOR 5 3 2 ------
Directional
Distribution
Directional
Distribution
Directional
Distribution
WEEKDAY
SATURDAY
SUNDAY
Looking North Looking South