Willowdale Intersection Assessment.pdfR.b,,, M. Hama., P.E_ P,T,O,E,, OW11o,
E HERMAN TRAFFIC ENGINEERING
TECHNICAL MEMORAN DU M
Date: October 13, 2008
From: Robert M. Herman, P.E., P.T.O.E.
Herman Traffic Engineering
To: Bob Murphy
Murphy Building Company, Inc.
Subject: Willowdale Townhomes
76th Ave. W./208th St. S.W. Intersection Assessment
'The proposed Willowdale Townhomes is a redevelopment of an existing office building site
located on the west side of 76th Ave, W. at the signalized intersection of 208th St. S.W. in the
City of Edmonds. Previously, ingress to the site was off of 76th Ave. W. just north of 208th St.
Southwest. Egress from the site was via the west leg of the 76th Ave. W./208 th St. S.W.
signalized intersection in an exit only configuration.
The existing 76th Ave. WJ208th St. S.W. intersection is a four -legged intersection. The north
and south legs consist of four lanes, two northbound and two southbound. The northbound
approach consists of a thru only lane and a right turn only lane. The southbound approach
consists of a left/thru shared lane and a thru only lane. The east leg consists of three lanes, a
left turn only lane, right turn only lane and a receiving lane. The west leg is a one lane
left/thru/right shared lane which is an exit only from the existing project site.
The existing traffic signal system is an actuated, permanent steel mast arm type system. The
existing traffic signal phasing is protected/permissive for the southbound left turn movement
and the eastbound and westbound approaches are split phased, meaning they operate
completely independently of one another.
The proposed Willowdale Townhomes site plan shows closure of the access north of the
intersection and modification of the exit only approach to the signalized intersection to allow
entering traffic as well as exiting traffic. The total width of the revised access will be 24 rnwl/
The intersection can be modified to accommodate the proposed two-way site access
configuration with the following comments and changes as shown on the attached figure:
1. The existing thru only arrow pavement markings on the southbound approach (cugrll,
lane) shall be modified to be thruffight shared arrows or removed entirely. The le
shared arrow pavement markings on the inside lane shall remain. Any existing ground -
mounted lane use control signage on the southbound approach shall be modified
accordingly.
425.277-1740 tel a 425-277-5718 fax
lite@comcast.net
15324 Southeast 133" Court, Renton, Washin-qton 98059
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76`h Ave. W./208th St. S.W. Intersection Assessment I E
October 13, 2008
Page -2-
2. The existing left only arrow pavement markings on the westbound approach (inside
lane) shall be modified to be left/thru shared arrows (total of two, but only one shown on
figure). The right only arrow pavement markings in the curb lane shall remain. Any
existing ground -mounted lane use control signage on the westbound approach shall be
modified accordingly.
3. The existing traffic signal heads facing the eastbound approach (site access) meet
MUTCD criteria for cone of visibility, being well under the 20 degree threshold at 1
degree (inside head) and 8.5 degrees (outside head).
4. Install 24"x36" R10-1201 "LEFT TURN MUST YIELD" sign on signal mast arm adjacent
to the inside signal head.
5. Replace existing signal mast arm -mounted sign with 30"x36" R3-6 left/thru shared lane
use control sign.
6. Install approximate 20 feet of double yellow centerline, preferably consisting of yellow
raised pavement markers, to discourage entering vehicles from crossing over the
outbound traffic signal detector loop on the site access and inputting a false call into the
traffic signal controller.
7. Install new induction loop vehicle detector per City standards. The loop should be
centered in the existing lane of the site access. Its location along the access will be
determined by the pedestrian crossing location and the stop line.
8. The existing signal standard on the northwest comer of the intersection will be close to
the new traveled way for the site access. Use AASHTO guidelines for clearance from
the traveled way to the face of the signal standard. In addition, use ADA guidelines to
ensure adequate ADA passage around the signal standard.
9. Remove existing thru only arrow pavement marking.
10. Remove existing left turn prohibition traffic sign from signal standard.
11. Remove existing "DO NOT ENTER" sign and post.
12. Modify or replace existing inside signal head to create the following signal indications
from top to bottom (all 12" indications): red ball, yellow ball, green ball, green left turn
arrow. Ensure signal head clearance to roadway is a minimum 16.5 feet, or City
standard clearance, whichever is greater.
13. Modify or replace existing inside signal head to create the following signal indications
from top to bottom (all 12" indications): red ball, yellow ball, green ball, green left turn
arrow. Ensure signal head clearance to roadway is a minimum 16.5 feet, or City
standard clearance, whichever is greater.
Please contact me at 425-277-1740 or hte@comcast.net if you have questions or if I can
provide additional information.
15324 Southeast 133" Court, Renton, Washington 98059 a 425-277-1740 tel 425-277-57113 fax
hte@comcast.net
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