23-101488_Sight Distance Analysis_3-22-23
Western Washington Division Eastern Washington Division
165 NE Juniper St., Ste 201, Issaquah, WA 98027 407 Swiftwater Blvd, Cle Elum, WA 98922
Phone: (425) 392-0250 Phone: (509) 674-7433
www.EncompassES.net
March 17, 2023
Mr. EJ Walsh
Public Works Director
Public Works Department
City of Federal Way
33325 8th Avenue South
Federal Way, WA 98003
Re: APL Short Plat – 2240 South 288th Street – Sight Distance Analysis at Proposed Site
Access
Dear Mr. Walsh,
The purpose of this letter is to present findings regarding the City’s request to evaluate the sight
distance conditions at the new proposed site access location for the APL Short Plat located at
2240 South 288th Street. As required by the approved Street Modification dated November 2,
2022 (Permit # 22-104775), an evaluation of intersection sight distance (ISD) has been completed
for the proposed joint-use driveway based on the City’s future Road Diet Project on South 288th
Street.
The proposed western access location has an intersection spacing from 23rd Pl S of 246.10 feet
and 47.46 feet of separation from the existing residential driveway to the west, which serves one
(1) single-family dwelling on the north side of S 288th St. The next public street intersection to
the west is at 22nd Ave S, which is located approximately 265 feet from the western shared
access location. See Exhibit A.
Per 19.135.280(2): Driveways that serve any use other than detached dwelling units may not be
located closer than 150 feet to any street intersection or any other driveway, whether on or off
the subject property. Driveways that serve only residential uses may not be located closer than
25 feet to any street intersection. The proposed joint-use driveway location meets the 150’
spacing from adjacent street intersections and the 25’ spacing from adjacent single-family
residential driveways.
With the proposed site access driveway located near the western property line of the project’s
property frontage along S 288th St, the intersection sight distance is adequate for all turning
movement conditions except for the left turn out when looking left (east) scenario. This scenario
is just 14’ short of meeting sight distance requirements for the left turn out condition. In order
to mitigate the substandard sight distance condition at the western access location, it is
APL Short Plat
Sight Distance Analysis
03/17/2023
Page 2 of 4
recommended that a “right turn only” sign be placed where the private access road exits onto S
288th St. See Exhibit A. Please refer to the analyses and conclusions on the following pages for
additional detail.
Note: all sight distance requirements are based on the 2018 AASHTO Green Book for the posted
speed limit of 35 mph on S 288th St and on the roadway profile of S 288th St obtained from the
original Sight Distance Analysis by William Popp Associates. The vertical curve element of the
profile was verified by William Popp Associates with a selected sight line evaluation and
comparison with the drawing profile.
Intersection Sight Distance (ISD)
The minimum acceptable values for intersection sight distance are shown in Table 3 based on
thew 2018 AASHTO Green Book. In computing and measuring intersection sight distance, the
height of the diver’s eye is assumed to be 3.5 feet above proposed access grade where the exiting
vehicle sits, and the height of the object to be seen by the driver is 3.5 feet. The location of the
driver’s eye is assumed to be 14.5 feet back from the edge of the major-road travelled way. Based
on the proposed access grade, the driveway elevation 14.5’ back from the face of curb is 474.30,
which is at the same elevation as the centerline profile of South 288th Street. Therefore, the
driver’s eye height is 477.80 at both locations.
Table 3
Intersection Sight Distance – 2018 AASHTO Green Book
Speed (mph) Movement Viewing
Direction
ISD (ft)
35 Left turn out from Driveway
(2018 AASHTO Table 9-7)
390
35 Right turn out from Driveway
(2018 AASHTO Table 9-9)
335
35 Left turn in from Major Road
(2018 AASHTO Table 9-17)
285
As shown in Table 3, AASHTO states the minimum required ISD for a left turn from stop onto a
two-lane roadway should be 390 feet (2018 AASHTO Table 9-7). Likewise the minimum required
ISD for a left turn from the two-lane road into the driveway should be 285 feet (2018 AASHTO
Table 9-17). The minimum required ISD for a right turn from stop onto a two-lane roadway is 335
feet (2018 AASHTO Table 9-17). Table 4 on the following page identifies the actual available
intersection sight distances for the three (3) sight distance conditions.
APL Short Plat
Sight Distance Analysis
03/17/2023
Page 3 of 4
Table 4
Intersection Sight Distance –
Driveway Movement Viewing Direction Required ISD (ft) Available ISD (ft)
Western
Driveway
Left turn out from Driveway
(2018 AASHTO Table 9-7)
390 600/376
Right turn out from Driveway
(2018 AASHTO Table 9-9)
335 376
Left turn in from Major Road
(2018 AASHTO Table 9-17)
285 376
As shown in Table 4, the western access location exceeds the minimum required ISD for all
conditions except for the left turn out looking to the left (east) condition. The western access
provides 376 FT of ISD when looking to the east, which is only 14 FT shy of the required minimum
of 390 feet for the left turn out condition. Profiles of the ISDs at each of the potential driveway
locations are shown on Exhibit B. Note that the results for the western access are shown in blue
font on Exhibit B.
Conclusions
With the proposed site access driveway located near the western property line of the project’s
property frontage along S 288th St, the intersection sight distance is adequate for all turning
movement conditions except for the left turn out when looking left (east) scenario. The available
sight distance in this direction is approximately 14 feet shy of the required minimum sight
distance.
In order to mitigate the substandard sight distance condition at the western access location, it is
recommended that a “right turn only” sign be placed where the private access road exits onto S
288th St. This concept is illustrated on Exhibit A.
Sincerely,
Encompass Engineering & Surveying, Inc. on behalf of American Pride Lending, LLC
Briana Bennington, PE
Project Engineer
03/17/2023
APL Short Plat
Sight Distance Analysis
03/17/2023
Page 4 of 4
Referenced:
CIP 95-07 (Table III-10 of the Federal Way Comprehensive Plan Chapter III)
S 288th St Road Diet webpage S 288th St Road Diet (16th Ave S to 34th Ave S) | City of Federal
Way
US Dept of Transportation Road Diets Notice Road Diets (Roadway Reconfiguration)
(cityoffederalway.com)
LUTC Agenda Packet 07/11/22 04-03-06 LUTC Agenda (cityoffederalway.com)
Site Distance Analysis by William Popp Associates dated July 12, 2006
Exhibits:
Exhibit A – West Access Site Plan – No Dedication
Exhibit B – SSD/ISD Sight Distance Profiles
Exhibit A
West Access Site Plan – No Dedication
23RD PLACE SOPEN SPACE/NGRA TRACTLOT 2LANDSCAPE TRACT20' ROW DEDICATIONS 288TH STACCESS /UTILITY TRACTLOT 1PARCEL AREA TABLESHEETAPPROVEDCHECKEDDRAWNDESIGNEDSCALEDATEJOB NO.REVISIONS A PORTION OF THE SE 1/4 OF SW 1/4 OF SECTION 33, T. 22 N., R. 04 E., W.M.CITY OF FEDERAL WAY, KING COUNTY, STATE OF WASHINGTONAMERICAN PRIDE LENDING LLC PRELIMINARY SHORT PLATEastern Washington Division
407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433
Western Washington Division
165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250Know what'sCallbelow.before you dig.RC-01AMERICAN PRIDE LENDING LLC
COVER SHEET & SITE PLAN
SIKANDER SEKHON (VSM)VICINITY MAPSITESITE DATA:PROJECT TEAM:UTILITY DISTRICT INFORMATION:EXISTING UTILITY NOTE:”””DATUM:BASIS OF BEARING:LEGAL DESCRIPTION:CONTRACTOR RESPONSIBILITY:DISCREPANCIES:BENCHMARK:NORTHFIRE NOTES:··REDUCED IMPERVIOUS SURFACE COVENANT NOTE:SHEET INDEXSheetNumberSheet TitleC-01COVER SHEET & SITE PLANC-02PRELIMINARY CLEARING, GRADING, & TREE RETENTIONPLANC-03PRELIMINARY DRAINAGE & UTILITY PLANA-01TREE RETENTION PLANA-02LANDSCAPE BUFFER PLANA-03LANDSCAPE DETAILSPROPOSED IMPERVIOUS SURFACE SUMMARY:GRADING VOLUMES5' BIKE LANE5' BIKE LANE5' BIKE LANE5' BIKE LANEWESTBOUNDTRAVEL LANEEASTBOUNDTRAVEL LANEWESTBOUNDTRAVEL LANEEASTBOUNDTRAVEL LANECENTER TURNLANENOT FOR CONSTRUCTION. FOR SIGHTDISTANCE ANALYSIS ONLY.
Exhibit B
SSD/ISD Sight Distance profiles
10'-0"376'-5 1/2"376' ISD (looking eastfrom west access)West Accessobject height (3.5') ISDISD --->eye height (3.5' abovedriveway/road grade)East Property LineSight Distance Exhibit Key:Western driveway Measurements (Blue font)Centered Access Measurements Source:William Popp Associates 7/12/2006