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Porphyry and Curbless Streets – Part 2

Porphyry stone pavers can be used on pedestrian surfaces, vehicle surfaces, as well as transition areas. This beautiful and sturdy stone will make any of these memorable. Special paving treatments can enhance the aesthetics of public spaces in a city, give circulation areas a stronger sense of place, and enhance the hierarchy of public spaces. 

In new street design, typically the decision to have curbed or uncurbed streets depends on the street’s desired traffic capacity and speed. In general, the higher the traffic speed and the less pedestrian-oriented the street is, the more likely that it will require a raised curbed street edge. Conversely, streets that have slower traffic and are more pedestrian friendly are good candidates for a curbless condition. Even commercial streets with on-street parking can be designed as curbless streets if there is enough right-of-way space and traffic speeds are relatively low. 

Festival Streets

Mercer Island Curbless Street used as periodic Festival StreetYou could always close a street and hold a festival, but then you say, “Hey – we’re in the street” But if you change the character of the street with stone pavers, no curbs and some well placed bollards, you close it and people say “hey –this is someplace special.

Porphyry Transition Area, Mercer Island WashingtonKPG, an interdisciplinary design firm provided design services for a curbless street/plaza in downtown Mercer Island, Washington. This corridor is the primary pedestrian corridor in downtown and terminates at the I-90 sculpture park.  KPG provided urban design, civil design, landscape architecture, utility design, traffic engineering and related services to create a pedestrian plaza street that allows auto access during the week and community/festival activities during the weekend or nights, as programmed by the City.


Shared Public Ways

Another approach is to create a permanently shared streetscape as opposed to periodic closure. The concept is called  “Shared Public Ways”.  San Francisco Better Streets has design guidelines for Shared Public Ways at the link below.

http://www.sfbetterstreets.org/design-guidelines/street-types/shared-public-ways/

Shared public ways should be designed to emphasize their pedestrian scale and calm traffic. They enable a generous pedestrian realm on narrow streets, and they create pockets of usable open space to act as front yards in open space-deficient neighborhoods.

Visual/Tactile Cues using Porphyry:

Variety of Stone treatments-Curbless StreetVisual/tactile cues should be provided to identify the presence of a shared public way as distinct from a traditional street, and to delineate between pedestrian-only and shared zones. Visual/tactile cues should be provided at all edges between pedestrian-only and shared zones, including from the crossing sidewalk. Visual/tactile cues should not impair the potential use of the entire right-of-way by all users.

A variety of materials, treatments and objects may be incorporated into creating visual/tactile cues. Combinations of elements may be used to create a more vibrant environment. Acceptable visual/tactile cues include but are not limited to the following:

changes of material texture (cobble or rough surfaces at shared zones contrasting to smoother surfaces at pedestrian–only zones, or use of cobbled stone bands between pedestrian–only and shared zones);

changes of material color and contrast (light on dark or dark on light);

Paving materials – Durable, textural material changes at the gateway to the shared public way, such as a band of rough cobblestones, storm drainage grates or textural material bands in pavement that provide a sense of low vibration when a vehicle drives over the material. Color and material contrast (light on dark, dark on light) can also distinguish changes between a standard street and the shared public way and send a cue to drivers that they are in a pedestrian-priority space and must slow down.

 

Porphyry’s composition determines its high compression strength, resistance to stains, slip resistance, and high freeze/thaw ratings.  The stone is the most popular paver in Europe, and is favored for its flexibility in design, beauty, durability and low maintenance requirements. ADA Compliant Porphyry pavers are also adaptable to a permeable paving set. The stone is by far one of the most durable pavers in the world.  These beautiful materials are available from Milestone Imports.   Milestone supports the creativity of architects, planners and designers. Porphyry offers surfaces of various finishes and mixed colorings, tending towards tones of grey, gold, violet and red, depending on where it is extracted.  The products are available in North America from Milestone Imports.  –  www.milestoneimports.com