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Rock Street, San Francisco

In an article by Queensland Transport (2005), it was explained that
pedestrian facilities that are designed for disabled people will also support
to the needs of other pedestrians, for example, parents using children’s
trolleys. People with disabilities and those without private vehicles mainly
have a smaller amount of access to many activities in the community and thus
make significantly fewer trips, especially in a car-dominated community.

An essential design element that is crucial to
accessibility is the curb zone. The curb zone is the primary barrier preventing
vehicles and other external elements such as water from invading the sidewalk
space. It indicates where the vehicle area ends and where the pedestrian area

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The ADA (Americans with Disabilities Act) has developed
design guidelines for pedestrian accessibility into buildings and facilities
along with the public right-of-way. These guidelines are named the ADA
Accessibility Guidelines (ADAAG). These guidelines cover the aspects related to
access to paths, roads, and facilities with applications to construction and

Curb extensions and ramps are essential design elements
required for appropriate pedestrian accessibility in the road network. Curb
extensions increase the range of the sidewalk towards the vehicular travel
lanes which reduces the street width but also improve the pedestrian crossing
and access by helping motorists and pedestrians see each other and reduce the
time that the pedestrians spend in the street. Vehicles are forced to slow down
and turn at slower speeds and prevents parking of vehicles close to
intersections. Curb extensions also provide spaces for curb ramps to be placed.
Curb Ramps enable walking pedestrians as well as others (Cyclists, Wheelchair
users) to move between streets and sidewalks. Figure (X) contains an image
showing the placement of curb ramps on the sidewalk curb extension for proper
accessibility of different pedestrians, wheelchair user, and cyclists from the
street zone into the pedestrian zone.









In the Planning and Urban Design
Standards (2007) book, the surface is described as the material that people
walk and wheel on inside the pedestrian environment. The type of surface
material affects the ease and means over which people can traverse. In general,
most sidewalk surfaces are asphalt or concrete and include bricks, stones and tiles.
Firm surfaces are necessary to prevent deformation and movement of materials by
the force applied by pedestrians and wheelchair users. Slip-resistant surfaces
prevent sliding of pedestrians and helps increase walking and wheelchair
safety.  The surfaces of the Sidewalks
contain the following design characteristics as prescribed by the Planning and
Urban Design Standards:


Grade: The grade is the slope that is corresponding to the travelled
direction on the sidewalk and is calculated by dividing the vertical change in
elevation by the horizontal distance covered. The change rate in grades are
measured using 61 centimeter intervals.


Width: Sidewalk widths are an important design element and effect
pedestrian usability and access type. The specified requirements for sidewalk
widths are named as “Design Width” and extend from the curb or planting strip
towards the buildings placed on the opposite side. Pedestrians require adequate
sidewalk widths in order to be separated from the mixed traffic on the other side
as well as clear distances from street furniture and other pedestrians with the
edges containing bus shelters and signs and utility poles. The distances that
pedestrians avoid to travel in are called ‘Shy Distances’. The space that
pedestrians feel comfortable travelling in is called ‘Effective Width’. The
Planning and Urban Design Standards Book indicates that from a 3.05-meter
sidewalk, only 1.83meters are for effective width with the rest being shy

distances. These elements can be
seen in figure (X).










Passing Space: According to the ADAAG, Passing Space is described as a section
of the pedestrian path that should be wide enough for people to pass 2
wheelchairs past each other with comfortability and ease. The source explained
how the passing space should be placed to allow 1 single wheelchair user to be
able to turn a complete circle with the appropriate ease.


Obstacle and Protruding Objects: Obstacles are defined as objects inside the pedestrian environment
that can cause limitations for the passage space of pedestrians and reduce
width of sidewalks. The Planning and Urban Design Standards Book (2007)
indicates that the pathways should be free from protruding objects as these
obstacles reduce the minimum required width and can cause serious walking and
wheelchair barriers. The following list describes the objects that can create
barriers for pedestrian travel if placed within the walking space: Awnings,
Bike Racks, Mailboxes’, Plants, Vending Machines, Signage and Poles Street
Furniture, Street Sculptures, Shelters, Trash Bins, and Informally Placed


Curb Ramps: Are mostly places at intersections and crossings and are designed
to decrease the grade and changes in level practiced by users. Curb ramps
contain the following elements: Landing, Approach, Flare, Ramp and Gutter.
Those elements can be seen in Figure (X).  Curb ramps are necessary for the access of
people with impairments in movement. According to the ADAAG, curb ramps should
be 0.91 meters wide.







Pervious Pavements: These
pavements effectively delay, treat and help with infiltrating the storm water
runoff in pedestrian spaces and surfaces. They can be placed for sidewalks,
furniture zones, cycling lanes and roadways. An example of a pervious pavement
application can be seen illustrated on figure (X).

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