In combination, transit-oriented development and green urbanism can deliver a powerful punch of energy self-sufficiency, zero-waste living, and sustainable mobility.
Transit-oriented development (TOD) has gained popularity as a sustainable form of urban growth. Creating a mix of mid-rise buildings and activities around a rail station, and interlacing the site with pedestrian amenities, is one of the best antidotes to car-dependent sprawl.
A new ultra–environmentally friendly version of transit-oriented development—green TOD—is taking form in several global cities. Green TOD is a marriage of TOD and green urbanism—a combination that can yield environmental benefits beyond the sum of what either can offer individually.
TOD helps shrink a city’s environmental footprint by reducing vehicle-miles traveled (VMT)—a direct correlate of energy consumption and tailpipe emissions. VMT declines not only from the shift of trips from auto to transit, but also replacement of auto trips to off-site destinations with on-site walking and cycling enabled by mixed land uses.
Green urbanism reduces nontransportation energy use, emissions, water pollution, and waste production through green architecture and sustainable community design. With green urbanism, pocket parks and community gardens replace asphalt parking. Renewable energy might come from solar and wind power, as well as biofuels created from organic waste and wastewater sludge. Insulation, triple-glazed windows, airtight construction, and use of low-impact building materials further shrink the environmental footprint of green TOD.
In combination, TOD and green urbanism can deliver a powerful punch of energy self-sufficiency, zero-waste living, and sustainable mobility.
Synergies from combining TOD and green urbanism are created in several ways.
Higher densities. The higher densities needed to fill the trains and buses that serve TOD also improve resource use efficiency. First, higher-density buildings have lower heating and cooling expenses from the embedded energy savings of shared-wall construction. For example, though Denmark and Finland have similar heating needs, the typical Danish urban household—living at densities that are about four times higher—consumes about 40 percent of the electricity of its Finnish counterpart. Second, higher densities support district heating/cooling and combined heat and power, two of the best ways to improve energy efficiency in buildings. Third, higher densities enable innovations that rely on volume. For example, producing renewable energy from wastewater or combustible waste is only possible in a high-density setting where large quantities of waste are produced in a small area. The financial savings from lower energy bills and reduced transportation costs can increase the demand for compact living.
Mixed land uses. The intermixing of housing, shops, restaurants, workplaces, and other uses places many destinations close together, thus inviting more walking and bicycling—not only to reach rail stops, but also to enjoy in-neighborhood shopping and socializing. Having both commercial and residential uses in proximity also allows the complementary heat and energy needs of commercial and residential spaces to be matched—for instance, for the use of waste heat to heat water. There is far more waste heat from commercial uses than there is demand for commercial hot water; adding adjacent residential space allows the reuse of a higher portion of commercial waste heat. Green TODs might also promote use of electric vehicles (EVs). Limited-range EVs can be used for a large share of trips in mixed-use settings, not unlike their use in golf-cart communities. One could imagine a future involving charging stations and electric-battery swap depots in eco-communities wrapped around rail stations.
Reduced surface parking and impervious surfaces. Surface parking, which consumes up to half the land in many U.S. suburban multifamily residential complexes, can be scaled back in high-quality transit settings and replaced by green space for play, socializing, and interaction among neighbors. Shrinking the footprint of parking reduces heat-island effects and water pollution from oil-stained runoff into nearby streams. The reduction of impervious concrete and asphalt surfaces helps recharge groundwater and replenish urban aquifers, thereby allowing greener and healthier gardens. Greater availability of homegrown produce increases food security and reduces the cost of and emissions required for transporting vegetables and fruits to markets.
Solar energy production at stations. Most surface train and bus depots have overhead canopies that provide shade and weather protection. Photovoltaic panels and even small wind turbines can be placed atop canopies at stops to generate electricity for transmission to surrounding homes and businesses through a smart grid. Solar energy can also power light-rail cars, as well as recharge batteries of plug-in hybrids at car-sharing depots and electric buses parked at stops during periods of low demand (as is currently done with Tindo solar-electric buses in Adelaide, Australia). The exteriors of peripheral parking structures can also provide a large expanse for solar power generation.
On the transportation side, green TOD can reduce VMT per capita by 40 to 50 percent compared with conventional suburban development. Green buildings and ecodesigns can reduce energy consumption and carbon emissions by stationary sources at even higher rates—50 to 60 percent compared with conventional development. With 32 percent of fossil fuel–generated carbon emissions by urban residents attributable to transportation and 27 percent linked to domestic household activities, it can be estimated that the combined effect of green TOD reduces carbon dioxide emissions by 24 to 29 percent compared with those of a typical car-oriented development.
Two European cities—Stockholm, Sweden, and Freiburg, Germany—have been environmental pacesetters and best personify the green TOD model. What green TOD neighborhoods in both cities have are not only ecofriendly designs, but also rail transit lines that run through the heart of communities, backed by high-quality services.
Development of Hammarby Sjöstad marked an abrupt shift in Stockholm’s urban planning practice. After decades during which new towns were built on greenfields, Hammarby Sjöstad is one of several “new towns in town” created following Stockholm’s 1999 city plan that set forth a vision of “Build the City Inwards.” Consisting of some 400 acres (160 ha) of brownfield redevelopment currently housing 20,000 residents and slated at buildout for 10,000 workers at its offices, shops, restaurants, and other businesses, Hammarby Sjöstad today stands as Stockholm’s largest urban regeneration project to date.
A tramway, Tvärbanan, runs through the heart of Hammarby Sjöstad. Six- to eight-story buildings are clustered along the transit spine, and building heights are tapered with distance from the rail line. Parks, walkways, and green spaces are also prominent throughout the development. Bike lanes run along major boulevards, all buildings have bike parking, and bike and pedestrian bridges span waterways. Parking is deemphasized: the project averages just 0.25 spaces per dwelling unit, well below rates found in surrounding suburbs. Moreover, all on-street spaces are metered and priced to discourage long-term parking. Hammarby Sjöstad’s location just outside Stockholm’s congestion toll boundary has prompted many of its residents to take public transit or walk or bike when heading to the central city.
Hammarby Sjöstad’s green urbanism is found in energy production, waste and water management, and building design. The energy use of buildings has been set at 5.6 kilowatt-hours per square foot (60 kWh per sq m), one-third less than for the city as a whole. All windows are triple glazed and walls are thoroughly insulated. Other conservation measures include extra heat insulation, on-demand ventilation, individual metering of heating and hot water use in apartments, lighting control, use of solar panels and fuel cells, reduced water flow, and low-flush toilets.
The ecological feature of Hammarby Sjöstad that has received the most attention is the fully integrated closed-loop ecocycle model. This system recycles waste and maximizes the reuse of waste energy and materials for heating, transportation, cooking, and electricity. At each building, residents can deposit waste into vacuum tubes that transport it to remote pickup locations. This minimizes truck traffic, thereby lowering emissions, as well as allowing narrower streets and less disruption from truck traffic. Waste is also converted into energy for district heating and cooling in the form of biogas created from treated wastewater—produced in the wastewater treatment plant from digestion of organic waste sludge—and though the incineration of combustible waste. In addition, biogas is used to run buses, and biogas-powered ovens are installed in about 1,000 apartments.
In 2002, when Hammarby Sjöstad was roughly half built out, it had already achieved a 39 percent reduction in air and water pollution and a 42 percent cut in nonrenewable energy use compared with communities in Greater Stockholm with similar household incomes. That same year, 52 percent of residents’ trips were by transit—well above the rate of other suburban neighborhoods, as well as inner-city Stockholm itself. One study estimated that residents’ carbon footprint from transportation in 2002 was roughly half that of those living in suburban communities with comparable incomes—966 pounds (438 kg) versus 2,012 pounds (913 kg) of CO2 equivalent per apartment per year.
Another measure of Hammarby Sjöstad’s success is its healthy local economy. In 2006, the district had a higher median household income and lower unemployment rate than Stockholm as a whole. Today, the district is abuzz with economic activity, with no signs of a blight that plagues many TODs in the United States—empty ground-floor retail space. Moreover, Hammarby Sjöstad’s land prices and rents have risen more rapidly in recent years than those in most other parts of metropolitan Stockholm. Today, Hammarby Sjöstad is considered a desirable address, reflected in comparatively high rents.
Freiburg’s Rieselfeld and Vauban Districts
The Rieselfeld and Vauban districts of Germany’s greenest city—the historic university town of Freiburg—were consciously designed to push the envelope of sustainable urbanism. Both are peripheral redevelopment sites linked to central Freiburg via the region’s tramway network. Both were built in the 1990s on less than 250 acres (100 ha) for 5,000 to 10,000 inhabitants. And both embody Freiburg’s aim of becoming a “city of short distances,” accomplished through mixed land use patterns and nearly ubiquitous public transit.
Rieselfeld and Vauban abide by Freiburg’s obligatory low-energy building standard of 6 kWh per square foot (65 kWh per sq m) per year—twice as efficient as Germany’s national energy standard. Both districts also generate heat and power through wood chip–fueled cogeneration plants, as well as exploit both active (through photovoltaics) and passive solar energy (through building orientation and architecture). In addition, both have comprehensive stormwater management systems that collect rainwater, maximize permeable surfaces through parks and playgrounds, and purify runoff through the use of bioswales and other soil filtration systems.
Rieselfeld is actually a transit-led development. A tramway extension to Rieselfeld opened in 1997, a year after the first families had moved in and when there were just 1,000 inhabitants. The presence of three tramway stations enabled urban growth to wrap itself around the rail nodes. With a maximum wait of seven minutes between trams, residents can reach Freiburg’s core within ten minutes.
Rieselfeld is also known for its barrier-free living environment, marked by high permeability and connectivity in its layout. It has an uncontrolled shared-space traffic system that sets maximum car speed at 19 miles per hour (30 kmph) and includes many shared “play streets” that give priority to children and pedestrians. Absent any stop signs, a yield-to-the-right system is used at intersections. Extensive bikeways and pedestrian ways help calm traffic, as does a grid pattern of narrow streets and intersection design that give priority to trams, buses, cyclists, and people on foot.
Vauban followed Rieselfeld’s ecofriendly design but upped the ante by creating a car-restricted community, in contrast to Rieselfeld, which averages one parking space per home. Cars are banned on most of Vauban’s streets. In addition to a 19-miles-per-hour speed limit on the main street, all other streets are designed for very-low-speed travel of three miles per hour (5 kmph). The town was laid out so that all residents live within two minutes of covered bike parking and five minutes of the tramway, which runs through the heart of the community.
Vauban’s planners went to great lengths to limit parking’s footprint. Seventy percent of housing units have no garage or driveway. Moreover, parking is unbundled from the price of a unit. In 2010, a parking space at one of the two shared garages on the town’s periphery cost €17,500 ($24,000). Both garages are topped by solar panels.
Today, only two of ten Vauban residents own a car, compared with 4.3 of ten Freiburg residents. Also, 57 percent of Vauban’s adult residents sold a car upon moving to the district. Most of Vauban’s residents buy a monthly transit pass, and half own a German National Rail Pass, compared with 10 percent of Germans nationwide.
Green TOD’s Widening Reach
Green TOD is beginning to catch on outside Europe. Recent green TOD plans have been developed for bus rapid transit and rail stations in Qingdao and Jiaxing, China, as well as in Kaohsiung, Taiwan. Perhaps the most ambitious version of green TOD is now taking shape in the deserts of the United Arab Emirates—at Masdar City outside Abu Dhabi. Besides being car free and interlaced by rail at the surface and by personal rapid transit and freight rapid transit below ground, Masdar City is to be fully energy self-sufficient, courtesy of a massive solar farm on the project’s edge. In addition, all organic waste is to be converted into biomass, all construction materials are being recycled, and over the long term, the project is to become completely carbon neutral.
Not all regions of the world are flush with oil revenues to bankroll green TODs, as is the case at Masdar City. An alternative funding approach is value capture. The degree to which green TODs create benefits is reflected in higher land prices, as experienced at Hammarby Sjöstad. Indeed, land sales were the principal means by which early rail systems were financed in the United States and much of Europe. Today, Hong Kong recaptures the added value from rail investments to cover more than 60 percent of construction costs, but also to finance upgrading and beautifying station areas with such amenities as public art, civic squares, streetscape enhancements, sidewalks, and bike lanes.
To the degree that green TODs shrink carbon footprints, market mechanisms and transfer schemes—whether in the form of revenue from a cap-and-trade system, impact-fee offsets, or property tax abatements —might be used to leverage them. Transfer payments—such as affordable housing setasides and density bonuses in return for below-market-rate housing—might also be used to reduce social inequities and displacement effects that invariably occur with urban improvement and gentrification.
Critics are apt to label green TOD as social engineering. In truth, many of those living in the suburbs of the world’s most car-dependent society, the United States, are living in engineered places—places that force people to drive to get from anywhere to everywhere. Green TODs provide consumers with more choices of where to live and how to travel. More choices and variety in urban landscapes are a good thing, especially given the increasingly diverse and plural makeup of households in America and other industrialized nations. Given the opportunity, more and more middle-class households will probably opt for green TODs for lifestyle reasons.
This article was excerpted from a 2010 research report titled “Toward Green TODs,” produced with funding support from the Berkeley Center for Future Urban Transportation, a Volvo Research Center of Excellence. The full report is available at www.its.berkeley.edu/publications.