Sustainable Streets
In mid July, I participated in two webinars that dealt with the sustainable design aspects of neighborhoods. Here, I will report on the first of them -- Technologies for Sustainable Streets. This was hosted by Ron Blank and Associates, and featured Landon Boone and Phil Sheldon.
Five areas make up the areas needed to be addressed when one designs for sustainable streets:
When choosing a paving material we need to consider how well the paving product can be recycled when it reaches the end of its useful life. Roads and side walks do NOT last forever. It may appear as a surprise that despite its apparent durability and dense nature, concrete is NOT a good candidate for recycling. Asphalt, on the other hand, is very easily recycled by simply milling it off the road surface and mixing it with new asphalt and bituminous material. In addition, concrete has a far higher carbon foot print than that of asphalt. In fact, asphalt has less than 60% of the carbon footprint of concrete, and is thus considered to be the greener of the two pavement choices.
Heat Island Effect is dramatically evident with pavement surfaces. In Vancouver, a study showed that the temperature of a developed paved area was 5 to 8 degrees hotter than an unpaved area nearby. This is where the concept of Solar Reflective Index (SRI) come in to play. A white surface has a SRI of 100, which means that it reflects 100 percent of the heat energy and absorbs none, while a total black surface is just the opposite. LEED requires that the SRI for paved surfaces be 29 or greater.
Just because dark surfaces are often preferred and even required in the design does not mean that we cannot get an SRI value greater than 29. While fresh asphalt has an SRI of only 5, and will have an average temperature of 123 degrees, and aged asphalt has an SRI of 10 with a temperature of 115 degrees, we can use proteolytic asphalt or coatings to get the SRI value up to 80 with an average temperature of less than 90. This really brings down the Heat Island Effect FAST. Even some of the dark colored asphalts have SRI values of over 30 when made with the proteolytic method. Dark surfaces are easier on the eyes, as they produce less glare. Thus, we can still use dark colors for pavement and see a temperature reduction of 15 degrees.
Volatile Organic Carbon (VOC) emissions also must be considered when specifying the paving material. California, a leader in environmental design, requires this value to be 100 or less. By using Advanced Acrylic coatings, we can get a VOC value of 21.
LEED for Neighborhood Development emphasizes three design areas: Smart location and linkage, Neighborhood Pattern and Design, and Green Construction and Design.
In the area of Smart Location, we take into account just how the location can utilize bicycle storage and network, as well as pedestrian access to all areas. These two items help to significantly reduce Vehicular Miles Traveled. There is also a Green Rating System for Roads that is similar to LEED in concept. Community outreach, tree-lined streets and Regional Priorities are emphasized in this system.
Life and Safety as well as Pedestrian Oriented Streets are a major goal in this effort. It is of interest that speed bumps do NOT work well to reduce traffic speed; people often just speed up after each bump. it has been found that reducing lane width has a far better effect. Also of value are traffic circles.
New York City, another leader in sustainable design and building codes, has done much in this area. They have reclaimed much space from vehicular traffic and provided it for pedestrian use on several of their main thoroughfares. These include Times Square, 57 and 34 Streets, as well as Broadway. In these reclaimed areas, one can now see a mall-like effect, with pedestrian walks as well as seating, which creates a park-like effect, while at the same time improves community linkage and pedestrian safety. In the paved areas, only low VOC pavement was used, and different colors for coatings were employed to make for easy and fast identification of these specific use locations. So far, the efforts have paid off with a 50% reduction in traffic accidents.
In the area of Neighborhood Identity, one can use Inlaid Durable Design Materials to create a means of identity and at the same time, unify a neighborhood. Cross walks can bear a logo or other means of specific community appeal.
Regarding the coatings that I mentioned above, they can last for two to 10 years, depending on traffic load, and road salt does NOT degrade them. (Snow plowing can ruin them, however.) Thus, one needs to take into account the traffic load VERY CAREFULLY when considering this type of pavement specification.
Five areas make up the areas needed to be addressed when one designs for sustainable streets:
- Environmentally Responsible Design
- Visually appealing and sense of community
- Durable and practical over life cycle of the pavement
- Safety
- Provide for Multiple Transport Modes
When choosing a paving material we need to consider how well the paving product can be recycled when it reaches the end of its useful life. Roads and side walks do NOT last forever. It may appear as a surprise that despite its apparent durability and dense nature, concrete is NOT a good candidate for recycling. Asphalt, on the other hand, is very easily recycled by simply milling it off the road surface and mixing it with new asphalt and bituminous material. In addition, concrete has a far higher carbon foot print than that of asphalt. In fact, asphalt has less than 60% of the carbon footprint of concrete, and is thus considered to be the greener of the two pavement choices.
Heat Island Effect is dramatically evident with pavement surfaces. In Vancouver, a study showed that the temperature of a developed paved area was 5 to 8 degrees hotter than an unpaved area nearby. This is where the concept of Solar Reflective Index (SRI) come in to play. A white surface has a SRI of 100, which means that it reflects 100 percent of the heat energy and absorbs none, while a total black surface is just the opposite. LEED requires that the SRI for paved surfaces be 29 or greater.
Just because dark surfaces are often preferred and even required in the design does not mean that we cannot get an SRI value greater than 29. While fresh asphalt has an SRI of only 5, and will have an average temperature of 123 degrees, and aged asphalt has an SRI of 10 with a temperature of 115 degrees, we can use proteolytic asphalt or coatings to get the SRI value up to 80 with an average temperature of less than 90. This really brings down the Heat Island Effect FAST. Even some of the dark colored asphalts have SRI values of over 30 when made with the proteolytic method. Dark surfaces are easier on the eyes, as they produce less glare. Thus, we can still use dark colors for pavement and see a temperature reduction of 15 degrees.
Volatile Organic Carbon (VOC) emissions also must be considered when specifying the paving material. California, a leader in environmental design, requires this value to be 100 or less. By using Advanced Acrylic coatings, we can get a VOC value of 21.
LEED for Neighborhood Development emphasizes three design areas: Smart location and linkage, Neighborhood Pattern and Design, and Green Construction and Design.
In the area of Smart Location, we take into account just how the location can utilize bicycle storage and network, as well as pedestrian access to all areas. These two items help to significantly reduce Vehicular Miles Traveled. There is also a Green Rating System for Roads that is similar to LEED in concept. Community outreach, tree-lined streets and Regional Priorities are emphasized in this system.
Life and Safety as well as Pedestrian Oriented Streets are a major goal in this effort. It is of interest that speed bumps do NOT work well to reduce traffic speed; people often just speed up after each bump. it has been found that reducing lane width has a far better effect. Also of value are traffic circles.
New York City, another leader in sustainable design and building codes, has done much in this area. They have reclaimed much space from vehicular traffic and provided it for pedestrian use on several of their main thoroughfares. These include Times Square, 57 and 34 Streets, as well as Broadway. In these reclaimed areas, one can now see a mall-like effect, with pedestrian walks as well as seating, which creates a park-like effect, while at the same time improves community linkage and pedestrian safety. In the paved areas, only low VOC pavement was used, and different colors for coatings were employed to make for easy and fast identification of these specific use locations. So far, the efforts have paid off with a 50% reduction in traffic accidents.
In the area of Neighborhood Identity, one can use Inlaid Durable Design Materials to create a means of identity and at the same time, unify a neighborhood. Cross walks can bear a logo or other means of specific community appeal.
Regarding the coatings that I mentioned above, they can last for two to 10 years, depending on traffic load, and road salt does NOT degrade them. (Snow plowing can ruin them, however.) Thus, one needs to take into account the traffic load VERY CAREFULLY when considering this type of pavement specification.
Posted by Alan L. Englander at 8/8/2010 1:10 PM 
Categories: Green Rating System for Roads, Life Cycle Cost, Neighborhood Identity, Multiple Transport Modes, Pedestrian Oriented Streets, Vehicular Miles Travelled, Recycleabiltiy of Paving Materials, Visually Appealing Design, Solar Reflective Index, Environmentally Responsible Design, Heat Island Effect
Categories: Green Rating System for Roads, Life Cycle Cost, Neighborhood Identity, Multiple Transport Modes, Pedestrian Oriented Streets, Vehicular Miles Travelled, Recycleabiltiy of Paving Materials, Visually Appealing Design, Solar Reflective Index, Environmentally Responsible Design, Heat Island Effect
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