Wednesday, February 7, 2018

Low Carbon Land Use: Paris, Pittsburgh, and the IPCC: Post 6: The Land Use Stabilization Wedge: Transportation: A Series by John R. Nolon

This post is the sixth in a series that will continue over the coming months.

Low Carbon Land Use: Paris, Pittsburgh, and the IPCC.

The Land Use Stabilization Wedge: Transportation

by John R. Nolon Distinguished Professor of Law

Elisabeth Haub School of Law at Pace University

The second slice of the land use stabilization wedge focuses on transportation, which accounts for over 70% of total demand for oil in the U.S. Americans drove over five million miles in 2014, 70% of that in personal vehicles, which contributes 20.5% of national CO2 emissions. Urban form and carbon emissions from vehicles are closely connected.  In a typical suburban neighborhood, for example, households may require up to 15 vehicle trips a day to commute to work, drive to school, and complete errands. This contrasts to many fewer vehicle trips daily where compact, mixed-use developments are required by local land use law.  Fewer trips translates into fewer vehicle miles travelled, which lowers CO2 emissions.

The Fifth Assessment Report of the IPCC, Chapter 12, targets the shaping of human settlements as a key to climate change mitigation.  It focuses on “the patterns and spatial arrangement of land use, transportation systems, and urban design elements, including the physical urban extent, layout of streets and buildings, as well as the internal configuration of settlements.” Chapter 12 also notes that “areas with a high mix of land uses encourage a mix of residential and retail activity and thus increase the area’s vitality and the aesthetic interest of the neighbourhood.” Land use regulations can ensure attractive buildings, personal neighborhood scales, and amenable green infrastructure. 

These fine points are critical.  Promoting compact, mixed use development by itself may not reduce driving much, particularly if the walking and biking options are not enticing. There is a current debate raging in the urban planning literature on this point, with recent statistical analyses suggesting less correlation between compact, mixed-use development and driving than previously posited.  Common sense and on-the-ground experience, however, make it clear that this type of development, enhanced by livable design, conveniently located shops and amenities, safe passage, and supportive infrastructure, lures many drivers from their cars and lowers trips and miles travelled significantly.  Little can be done to reduce emissions from personal travel without this type of neighborhood development.

The successful development of transit stations and rail and bus lines is dependent upon land use densities and mixed use development. There must be a large enough number of commuters in a transit station area to provide a base level of ridership. In addition, ridership must be sufficiently diverse to ensure that people are traveling to work, to shop, to seek entertainment, and to go home at various times during the day, thereby increasing the cost efficiency of the transit system.

Local land use plans and zoning, which determine population density and building uses, control how much the population will increase over time in a certain area, and what transportation needs new people will have.  This, in turn, dictates the demand for various types of transportation services.  Locally, this planning is done at the neighborhood level and should be guided by objectives contained in the city-wide comprehensive plan.  To make transit systems feasible, land use planning among localities must be coordinated with regional transportation planning and development, which occurs under federal programs in urban areas at the metropolitan-area level.

Even where communities are not served by transit systems, local leaders can create compact, mixed use neighborhoods that reduce car trips and miles traveled.  Zoning controls can limit the size of housing units and combine retail, office, and residential land uses, putting services, shops, and jobs in closer proximity to homes.  Communities not yet served by transit can designate one or more priority growth districts and create overlay zones for them that allow greater densities and more land uses than permitted in the underlying zoning districts.  By clustering development strategically, these growing localities position themselves for future service by commuter rail or bus rapid transit, thereby becoming “transit ready.”

Suburban areas that adopt higher-density, mixed-use zoning will find it easier politically to adopt strong environmental protection ordinances applicable to the land outside high-density zones.  Where state law permits, density bonuses may be provided in denser suburban zones and cash contributions made by developers in exchange.  This money can be used to purchase development rights from landowners in sensitive environmental areas outside the higher-density zone, areas that mitigate climate change through biological sequestration.  This balance between development and conservation can be accomplished within transit-served urban areas as well – highlighting again zoning’s ability to create sustainable settlement patterns and to mitigate climate change.

The strategies described here are generally divided into urban, transit-served neighborhoods, or Transit Oriented Development and denser mixed-use suburban neighborhoods without transit, referred to as Transportation Efficient Development. One of the corollary benefits of concentrating development in these ways is the preservation of surrounding open spaces which enhances sequestration, another mitigation strategy that will be taken up in the next blog. See Climate Change, Zoning and Transportation Planning: Urbanization as a Response to Carbon Loading.

Material from this series will appear in Low Carbon Land Use: Paris, Pittsburgh, and the IPCC, an article to be published by the Arkansas Law Review.

Previous posts in this series are available here:

Post 1:  Paris, Pittsburgh, and the IPCC

Post 2:  Post-Paris Contagion

Post 3: Carbon Emissions: The Land Use Connection

Post 4:  Shaping Human Settlements

Post 5:  The Land Use Stabilization Wedge: Buildings

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"There is a current debate raging in the urban planning literature on this point, with recent statistical analyses suggesting less correlation between compact, mixed-use development and driving than previously posited. " Could you provide links to some of the relevant literature?

Posted by: M. Mayer | Feb 16, 2018 12:25:57 PM