§ 270.2.



Findings. The historically industrial parts of the City, including the South of Market, Showplace Square, Central Waterfront, and Mission, typically have very large blocks. In the South of Market, a typical block is 825 feet in length and 550 feet in width; in Showplace Square and the Central Waterfront blocks extend up to 800 feet in length and greater; and in the Mission many blocks are over 500 feet in length. In areas of the City historically developed as moderate and high-density residential and commercial environments, the block pattern is much smaller, with many alternate and redundant paths of travels, service alleys, and public mid-block pedestrian walkways and stairways: the typical North of Market block is 275 feet in width and not more than 412.5 feet in length, often with minor alleys bisecting these blocks further into smaller increments.

Large blocks inhibit pedestrian movement and convenience by significantly lengthening walking distances between points, thereby reducing the ability and likelihood of people to walk between destinations, including reducing access to and likelihood of using transit. Academic studies have shown that the likelihood of people to walk for trips of all purposes, including walking to transit stops, declines substantially above distances as low as 1/5th of a mile, and that the propensity to walk is very elastic for distances of one mile or less and heavily dependent on distance and route barriers (Berman, Journal of American Planning Literature, May 1996). People are generally willing to walk not more than 1/3-mile to access rail transit, and less to access bus transit. In the Eastern Neighborhoods Mixed Use, South of Market Mixed Use, C-M, and DTR Districts, and South-of-Market portion of the C-3 Districts, longer walking distances due to large blocks generally lengthen walking distances by up to 1,000 feet or more for even the shortest trips, a major factor in reduced use of transit in these areas. In areas with large blocks, walking distances between destinations can be between 50% and 300% longer than for areas with smaller blocks and more route choices (Hess, Places, Summer 1997). In the South of Market area, for example, the distance between destinations for walking trips can be as much as 2.5 times longer than a trip between destinations similarly situated apart north of Market Street. Given equivalent densities and distributions of development, where walking distances are greater due to longer and larger blocks, residents have access to up to 50% fewer destinations (e.g. shops, services, transit) for equal walking distances (ld.). Greater walking distances and fewer route choices also severely degrade accessibility to transit, services, and shops for people with disabilities and the elderly (Kulash, Development, July/August 1990). Because there are fewer pedestrian route choices and people must walk on fewer, more-highly trafficked and busier streets for longer distances, the quality of the pedestrian experience is severely diminished and there are more conflicts with motor vehicles, with corresponding heightened concerns for pedestrian safety on major streets.

Large blocks also increase vehicular and service demand on streets. Where there are no secondary streets or service alleys, all vehicular functions (including service loading as well as private vehicular access to off-street parking) are concentrated onto fewer streets, increasing traffic volumes on these streets and creating significant and frequent conflicts with automobile traffic, transit, bicycles, and pedestrian activity.

Where industrial uses with low densities of workers and residents remain in place, the condition of large blocks is not a problem. However, where land use changes occur with new development and the intensity and density of residential and employment population are increased by new development, there is thus a significant new need created to improve pedestrian and vehicular circulation by mitigating the size the blocks, providing alternate and redundant paths of travel, and creating a more pedestrian-accessible environment.


Purpose. The mid-block alley requirements of this Section are intended to ameliorate the conditions and impacts described in the Findings of subsection (a) above and make the subject areas appropriate for a higher density of activity and population in areas being targeted for more intense development.


Applicability. This Section applies to all new construction on parcels that have one or more street frontages of over 200 linear feet on a block face longer than 400 feet between intersections, and are in the C-3 Districts, C-M Districts, in South of Market Mixed Use Districts, Eastern Neighborhoods Mixed Use Districts, or DTR Districts, except for parcels in the RH DTR District, which are subject to Section 827.




New construction on lots with greater than 300 linear feet of street frontage shall provide a publicly-accessible mid-block alley for the entire depth of the property, generally located toward the middle of the subject block face, perpendicular to the subject frontage and connecting to any existing streets and alleys. For development lots with frontage on more than one street that exceeds the above dimensions, one such mid-block alley will be required per frontage.


For new construction on lots with frontage greater than 200 linear feet but less than 300 feet the project shall provide a publicly-accessible mid-block alley for the entire depth of the property where any of the following criteria are met:


There is an opportunity to establish a through-block connection between two existing alleys or streets, or


A portion of the subject frontage extends over the central half of the block face, or


Where it is deemed necessary by the Planning Department and Commission to introduce alleys to reduce the scale of large development, particularly in areas with a surrounding pattern of alleys.


Design and Performance Standards. The alleys provided per subsections (a) and (b) above shall meet the following standards:


Generally be located as close to the middle portion of the subject block face as possible, perpendicular to the subject frontage and connect to existing adjacent streets and alleys;


Provide pedestrian access;


Provide no, limited or full vehicular access, as specific conditions warrant;


Have a minimum width of 20 feet from building face to building face, exclusive of those obstructions allowed pursuant to Section 136, and a minimum clearance height from grade of 15 feet at all points. In RED, RED-MX, WMUG, WMUO, and SALI Districts, the minimum width shall be 30 feet;


Have a minimum clear walking width of 10 feet free of any obstructions in the case of a pedestrian-only right-of-way, and dual sidewalks each of not less than 6 feet in width with not less than 4 feet minimum clear walking width in the case of an alley with vehicular access;


In the Eastern Neighborhoods Mixed Use Districts, be at least 60% open to the sky, including those encroachments permitted in front setbacks by Section 136 of this Code;


Provide such ingress and egress as will make the area easily accessible to the general public;


Be protected from uncomfortable wind, as called for elsewhere in this Code;


Be ungated and publicly accessible 24 hours per day, as defined elsewhere in this Section;


Be provided with appropriate paving, furniture, and other amenities that encourage pedestrian use, and be landscaped to greatest extent feasible;


Be provided with ample pedestrian lighting to ensure pedestrian comfort and safety;


Be free of any changes in grade or steps not required by the underlying natural topography and average grade; and


Be fronted by active ground floor uses, as defined in Section 145.1, to the extent feasible.


New buildings abutting mid-block alleys provided pursuant to this Section 270.2 shall feature upper story setbacks according to the provisions of Section 261.1.


Maintenance. Mid-block paths and alleys required under this Section shall be maintained at no public expense. The owner of the property on which the alley is located shall maintain it by keeping the area clean and free of litter and by keeping it in an acceptable state of repair. Conditions intended to assure continued maintenance of the right-of-way for the actual lifetime of the building giving rise to the open space requirement may be imposed in accordance with the provisions of Section 309.1 for DTR or 329 for Eastern Neighborhoods Mixed Use Districts.


Informational Plaque. Prior to issuance of a permit of occupancy, a plaque shall be placed in a publicly conspicuous location for pedestrian viewing. The plaque shall state the right of the public to pass through the alley and stating the name and address of the owner or owner’s agent responsible for maintenance. The plague shall be of no less than 24 inches by 36 inches in size.


Property owners providing a pathway or alley under this section will hold harmless the City and County of San Francisco, its officers, agents and employees, from any damage or injury caused by the design, construction or maintenance of the right-of-way, and are solely liable for any damage or loss occasioned by any act or neglect in respect to the design, construction or maintenance of the right-of-way.


Any non-vehicular portions of such a pathway or alley, including sidewalks or other walking areas, seating areas, or landscaping, may count toward any open space requirements of this Code which permit publicly-accessible open space, provided that such space meets the standards of Section 135. In C-3 Districts, the non-vehicular portions of such a pathway or alley may count towards the open space requirements of Section 138 of this Code, so long as the pathway or alley is located at street grade and meets the requirements of Section 138 and of this Section.



(Added by Ord. 298-08, File No. 081153, App. 12/19/2008; amended by Ord. 85-10, File No. 091271, App. 4/30/2010; Ord. 42-13 , File No. 130002, App. 3/28/2013, Eff. 4/27/2013)

Division (e)(4) amended; Ord. 42-13 , Eff. 4/27/2013.


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