HomeMy WebLinkAboutAgenda Bill 7.A-Attch09 09/13/2004ATTACHMENT 9
W1 - LSON
ENGINEERING
Ms. Maria Ponce].
te TRANSPOWIAIAON West 'Bay Builders
CONSAMAKNTS, IN(:
From: John Wilson
Date: July 27, 2004
MEMORANDUM: E_4VA
A L 1 G 9 - 6 20 0j 4
RE: Revised Analysis of Diagonal Parking on Keller 'Street
As I have indicated in previous discussions and. e-mmails, I would suggest that the
city move slowly when Considering the proposal to change parking on the westerly
side of Keller between Oak and the southerly edge of the 'Sweed School site from
parallel to diagonal'. In general, angled parking can be an effective way to slow
CIVIL ENGINEERING traffic while increasing the on-street. parking inventory. If there aren't too many
curb cuts (Orive'W'a,ys etc.) such as is the case at this location, typically more
TRAFFIC IMPACT diagonal spaces can be provided versus parallel spaces. In terms of slowing traffic,
STUDIES
the basic Maneuver of having to back out of an angled space and then changing
TRANSPORTATIION directions to pull away is. generally more disruptive to: theflow of through traffic on
PLANNNG
the street relative to pulling forward out of a parallel- space In a single maneuver.
TRAFFIC SIGNAL The presence: of angled parking can also lend a sense of increased risk for through
DESIGN
traffic causing drivers to slowdown for this perceived potential for safety hazards.
The biggest drawback to changing to angled parking is this potential reduction in
traffic, safety being real. The degree of impact to traffic safety is intuitively a
function of vehicle speeds, traffic: volumes, parking, angle,. parking space widths,
70 ZOE STREET number, of parking maneuvers, traveled way widths,. etc. Items impacting bicycle
and vehicle Safety include the speed of through traffic, the width of the traveled
SUITE 200 way, the extent vehicles out encroach intolravel lanes, parking turnover
SAN FRANCISCO, CA rates, et ' c. The presence of bicycles only compounds this. In I this case, Keller Street
has a curb to curb Width of 46 feet. Use of 8 feet for.parallel parking on the east
TEL: (415) 974-5071 side leaves 36 f6et for two-way traffic and some type of.parking,on the westerly
FAX. (415) 974-5073 side of the street. Typically travel,lanes are 12 feet. wide which would leave a total
EMAIL, -WESFCA@AOL.COM of 12 feet available P6r on - street parking on the west side. However, diagonal
parkin'g, depending upon the angle, requires , a minimum of between 14-16 feet for
30 degree., parkin&and 1748 feet for 45 or 60 degree parking,, as indicated in the
attached Figures 1 through 3. This in turn will require a reduction in travel lane
widths (desirable from the perspective of slowing down.through traffic) to 10 to 12
feet. Use of 18 feet of street width to accommodate 45 or 60 degree diagonal
parking on the west . side, leaves a two-way, travel way, width of 20 feet which is
relatively narrow for two-way traffic, even without the presence of bicycles. The
limited travel width allows essentially no room for bicycles when through traffic
•
maria,poncel
Jul' 28, 2004
Page 2
With regard to edge striping on, Liberty Street, this.clould:possibly provide some help
slowing down traffic and.'proihofing g
eneral vi'sibility bybelping to k.eeg
'traffic towards the: center of the street.
Attachments
•
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