HomeMy WebLinkAboutAgenda Bill 7.A-Attch12 09/13/2004lib
Additional" Correspondence
e
MEMORANDUM
WILSON
INGINLE
& - R A NS P 0 RTATI ON
C - ,qNSULA - A: , (_I�S. INC
To: Ms., Maria Poncel
West, Bay'Builders
From; John Wilson
p1`
`004
0 11. �O - 9
CIVIL ENGINEERIN.G
TRAFFIC IMPACT
STUDIES
TRANSPORTATION
PLANNING
TRAFFIC SIGNAL
DESIGN
70 ZOE STREET
SUITE 200
SAN FRANCISCO, CA
94 107
TEL: (41 974-5071
FAX: (4 15) 974-5073
Date: Septeitiber 9 - 2004
ri
RE: Sweed-_ School — Liberty Street Driveway Sight Distance
The current. site includes two single car garages with driveway access
to Liberty Stroet, one at the north end of the site. and ithe: second at the south end of
the site. The 9-foot wide driveways are° located approximately 7 feet from the
respective property lines A review of sight distance for ilieAriveways indicated
the critical issue is sight lines to,the, south of the project relative to northbound
traffic on, Liberty Street. 'Can northbound vehicles see vehicles backing out of a
driveway and vice Verse,?
Sight distance, measurements typically assume a. dn'ver eye height of 3.5 feet
(Highway Design Man ual, Cafir'ans, 5 Editions A Policy on Geometric Design of
Highways and Streets, AASHTO, 1090). The object.heiglit (an object in the street
which can damage an auto) is considered to be 6` inches , if one is concerned about a
rock, smallanimall or othertypes of debris. If the object of concern is another
automobile, ,a 2 1/2 or 2 -foot. height to taillights would be sufficient (A Policy on
Geometric Design offghwap and Streets, AASHT0, 1_990,)'. The minimum
stopping sight distance standard for a 25 ' MPH speed on wet pavement is 150 feet
(Caltrans & AASHTO). The measured northbound sight distance to the northerly
driveway is in - excess , of,200 feet,regaTdless of object height. The northbound sight
distance to the southerly !driv
-is 149-150 feet assuming; a 6 inch high object
and 1,83,fe.et, assuming an Nect heig g ht of 2 fee (oncoming headlights or tail lights
of someone backing out of ihe southerly driveway
Sight distance to. both, driveways for southbound drivers on Liberty Street is well in
excess -of.minimum 2 - MPH distances.
EMAIL: WESFCA(,)AOL.COM