These are effects that a transportation project has on adjacent neighborhoods and communities, beyond those intentionally affecting travelers and direct users of the transportation facilities. Often called "community impacts" or "social impacts," they affect neighborhood livability (the quality of the local environment as experienced by people who live, work or visit there) as a consequence of changes in noise, views, walking environment, land use mix and community cohesion (the quality of interactions among neighbors). Related impacts on property values can also be included, and differential impacts on vulnerable population groups may also be covered.
A new highway interchange directly requires that some households and businesses be relocated (displacement effect).
A new or wider roadway creates a barrier to walking and cycling (called the barrier effect) , dividing a neighborhood and increasing the need to drive, for example, forcing parents to chauffeur children to school.
A new transit terminal reduces sunlight and blocks views for a section of the neighborhood (visual effect).
Converting a road with at-grade intersections to an expressway with limited access diminishes access to businesses and households located between the interchanges (accessibility effect).
Improving walking and cycling conditions in an area, and incorporating features such as walkways and pocket parks, improves opportunities for neighbors to meet (increased community cohesion).
Roadway reconfiguration makes it possible to locate new offices and shops in a depressed neighborhood as a consequence of improvements in safety and ease of access (land use and property value effects).
Relationship to Transportation System Benefit-Cost
Most "community impacts" are "externalities" — impacts outside of the intentional costs of the transportation project and outside of the intentional direct benefits to users of the transportation system. Community impacts are sometimes grouped with economic development impacts under the broader category of "social and economic impacts." However, the two are frequently examined separately because community impacts are typically more localized (focusing on the everyday lives of people in adjacent neighborhoods) and typically measured in more qualitative terms. Community impact can be an important consideration when transportation decision-makers are weighing the positive, negative, and distributional effects of proposed projects. However, since community impacts are generally qualitative and subject to judgment, they are typically considered part of the "environment impact assessment" process rather than included as monetary measures in benefit-cost ratios. One accepted way to consider community impacts in a quantitative way is to include them alongside quantitative user benefit measures in "multiple accounts valuations" or other related appraisal systems that line up all positive and negative impacts and apply some sort of score or weight to them. The US Dept. of Transportation has a guide to Community Impact Assessment (CIA) and frequently sponsors workshops on the topic. The National Cooperative Highway Research Program has a guide to measuring social and economic impacts of transportation, which defines key elements of community impacts and discusses methods for measuring them (Forkenbrock and Weisbrod, 2001). Much of the discussion below is drawn from that document.
Displacement and Barrier Effects
"Community cohesion" is an urban planning term for patterns of social networking within a neighborhood or community. The impacts of transportation projects on community cohesion "may be beneficial or adverse, and may include splitting neighborhoods, isolating a portion of a neighborhood or an ethnic group, generating new development, changing property values, or separating residents from community facilities" (FHWA 1987). Displacement of businesses and residences resulting from a transportation project is an important related impact. Estimates of the extent to which a proposed transportation project may affect community cohesion rely heavily on site analysis, self-reporting, and survey analysis. Measuring the changes in community cohesion resulting from a transportation project requires documenting existing patterns of community social networking (base case) and then estimating the potential reduction of or increase in community interaction if the proposed project were built. It is important to note that this impact category does not lend itself to quantitative measures, and these impacts also overlap with several other impact categories (e.g., safety, noise, or distributive effects).
The Barrier Effect (also called severance) refers to delays, discomfort and lack of access that vehicle traffic imposes on nonmotorized modes (pedestrians and cyclists). Severance usually focuses on the impacts of new or wider highways, while the barrier effect takes into account the impacts of vehicle traffic.The barrier effect is equivalent to traffic congestion costs (most traffic congestion cost estimates exclude impacts on nonmotorized travel). In addition to travel delays, vehicle traffic imposes crash risk and pollution on nonmotorized travelers. The barrier effect reflects a degradation of the nonmotorized travel environment. This is not to imply that drivers intentionally cause harm, but rather that such impacts are unavoidable when, heavy and hard vehicles traveling at high speed share space with vulnerable road users.
The barrier effect imposes indirect costs by reducing the viability of nonmotorized travel, which reduces accessibility for non-drivers, and causes shifts from nonmotorized to motorized travel which increases external costs such as traffic congestion, parking costs and pollution emissions. It tends to be inequitable because disadvantaged populations tend to bear a disproportionate share of this cost since they often depend heavily on nonmotorized transport. Various methods are used to quantify and monetize barrier effect costs (DfT 2009; Litman 2009; NZTA 2010)
Transportation projects can cause a significant visual effect on the surrounding built environment when they involve the building of new structures, tearing down old ones, or removal of landscaping and vegetation. Undesirable effects include obscuring views of pleasant landscapes or the night sky. On the other hand, construction associated with transportation projects can have the desirable effect of eliminating neighborhood "eyesores," and a well-designed transportation structure, such as a new bridge, can become a landmark and enhance the visual environment. Depending on the outcome, nearby locations will be more or less attractive as places to live or work. The visual impacts of a project can be estimated by using various simulation techniques to create the different possible views and then surveying area residents for their reactions. More quantitative measures of the visual effect of a project can be accomplished by systematically assessing separate components that affect the visual quality of a transportation facility and its surrounding environment. These elements are defined in different ways by Rahman (1992) and Lynch (1960).
In general, accessibility measures the relative ease with which desired destinations can be reached. For individuals and households, access to important lifestyle destinations (i.e., work, recreation, family and friends, houses of worship, and shopping) is a vital element of overall quality of life. For businesses, good accessibility to workers, suppliers, and markets is essential to operate competitively. A transportation project may substantially improve the accessibility of some locations and reduce the accessibility of others. A location can be quite accessible by auto, but difficult to reach for travelers without a car. It is important to distinguish accessibility from mobility, which is the ability of someone to move around. Accessibility is defined in terms of a specific impact area. As a derivative of transportation impacts, accessibility is most often judged on the basis of the changes in time and cost to travel to and from a given location and the breadth of destinations or market reach that it enjoys.
A transportation project may lead to changes in the intensity and mix of use for neighboring real property (land and the buildings on them). This occurs in part as a direct consequence of changes in land taken up by the transportation facilities, such as roads, transit stations, and supporting vehicle storage and maintenance facilities. It also occurs as an indirect consequence of changes in accessibility — which may encourage changes in density of land development, extent of open space and mix of uses (residential, retail, office, industrial, park, and so on).Land use density changes may, in turn, have further consequences for the operating costs of government, households, and businesses. There is a substantial line of research on the social and economic costs of sprawl, though there is no consensus on the valuation of those impacts nor on the extent to which various types of transportation projects may encourage or discourage sprawl. Also, some of the land threatened by sprawl, such as wildlife habitats and wetlands, may have greater ecological than economic value. A summary of the literature on land use and related costs is provided in Litman (2003).Keep in mind that transportation investments do not always change land use patterns. For example, if a new transit system is meant to encourage higher-density land use, the system must be located where there is potential for development; also, the city or county would need to increase density around transit stops, which is often unpopular with nearby residents.
A transportation project may lead to subsequent changes in the value as well as use of surrounding real property (land and the buildings on them). Property values are most often measured in terms of the average price for a specific type of land. Within most urbanized areas and in some rural areas, there are constraints on the allowable use for specific parcels of land, so transportation projects tend to affect both the value of land and the intensity of its use simultaneously. Property values and land use patterns both reflect changes in the same basic factor — the locational pattern of demand for real property. If a place becomes more desirable for people as a place to live, or for businesses as a place to operate, then demand for that location would increase as more people or businesses desire to locate there, and property values would be driven up. Changes in property values are a direct measure of shifts in demand for a location, and thus they represent a leading indicator of subsequent changes in the intensity of land use. To the owners, though, property value impacts also represent a change in personal wealth. Property values, like land use changes, are actually results of other impacts. In other words, changes in property values are driven by, and hence reflect, the value associated with local changes in community impacts (accessibility, safety, noise, visual amenity, and community cohesion), as well as economic development impacts (business productivity). In general, a transportation project would only lead to changes in property values (and subsequent land use) if it causes a direct change in one or more of these other local factors that affect the desirability of a location. That is why economists view changes in property values as the "capitalized valuation" of other local factors, and note that it would be "double counting" to add the dollar value of property impacts on top of the dollar value of other economic (and social) impacts. Recent studies on property value impacts include Cervero (1997) and Ryan (1999). More general resources and overviews of literature on property value impacts are provided in Forkenbrock and Weisbrod (2001) and Litman (2003).
Civic Pride Effect
Some transportation investments — such as rail transit systems, freeways, airports, and train stations — are sometimes justified in part because local citizens see them as a symbol of a progressive community. In theory, that could enhance the quality of life for local residents, enhance the ability of the community to attract new business investment, and ultimately also raise property values. Such consequences are of course far from guaranteed, and the likelihood of them occurring is also difficult to measure. However, it is basically up to local decision-makers to choose how to make trade-offs between these types of factors and the costs involved. In any case, they are outside the realm of benefit-cost calculations.
Distributive effects (also called equity impacts) refer to the distribution (or incidence) of impacts and the degree that is considered appropriate. These differences can occur in terms of who receives transportation user benefits, who pays the costs of projects, and who bears the brunt of negative externality impacts. While "benefit-cost analysis" measures the efficiency of spending on transportation projects, "distributive equity" measures the fairness of the allocation of costs, benefits, and other consequences. "Environmental justice" is a related legal term, referring to a body of federal law and regulation that prohibits projects from focusing their negative impacts on low income, minority and vulnerable population groups.Of greatest relevance to benefit-cost analysis is concern over the possibility of a "mismatch" between the incidence of costs and benefits. The NCHRP Guide to Social and Economic Effects (Forkenbrock and Weisbrod, 2001) provides discussion of various ways to measure equity. The issue is important because, as noted in that report, "Changes in transportation systems are like almost any other type of government project: the beneficiaries of a particular project may be difficult to identify because they are dispersed across a region. But the negatives associated with the projects—the noise, community disruption, and other effects… usually occur along a relatively narrow area immediately adjacent to the facility. Even when a project provides net gains across a region, the relative benefits and costs accruing to individuals and groups within the region vary such that those who must tolerate the worst effects may not be enjoying benefits commensurate with the costs they bear."
AARP (2008), Opportunities for Creating Livable Communities, Research Report, American Association for Retired Persons Public Policy Institute (www.aarp.org/ppi); at www.aarp.org/research/housing-mobility/indliving/inb155_communities.html.
AIA (2005), What Makes a Community Livable? Livability 101, American Institute of Architects (www.aia.org); at www.aia.org/aiaucmp/groups/aia/documents/pdf/aias077949.pdf.
Christopher Alexander, et al (1997), A Pattern Language, Oxford University Press (New York).
Heather Allen (2008), Sit Next To Someone Different Every Day - How Public Transport Contributes To Inclusive Communities, Thredbo Conference (www.thredbo.itls.usyd.edu.au); at www.thredbo.itls.usyd.edu.au/downloads/thredbo10_papers/thredbo10-plenary-Allen.pdf.
Bruce S. Appleyard (2011), Street Conflict, Power and Promise: Humanising the Auto-Mobility Paradigm, foreword for the Second Edition of Livable Streets; World Transport, Policy & Practice, Vol. 17.2 (www.eco-logica.co.uk); at www.eco-logica.co.uk/pdf/wtpp17.2.pdf.
Robert Cervero (1997), "Transit-Induced Accessibility and Agglomeration Benefits: A Land Market Evaluation," Institute of Urban and Regional Development, University of California at Berkeley.
Complete Streets (www.completestreets.org) is a campaign to promote roadway designs that effectively accommodate multiple modes and support local planning objectives.
CTE (Center for Transportation and the Environment) (2008), Improved Methods For Assessing Social, Cultural, And Economic Effects Of Transportation Projects, NCHRP Project 08-36, Task 66, Transportation Research Board (www.trb.org) and American Association of State Highway and Transportation Officials (AASHTO); at www.statewideplanning.org/_resources/234_NCHRP-8-36-66.pdf.
DEA & Associates (1999), Main Street…When a Highway Runs Through It, Transportation and Growth Management Program, Oregon DOT and Dept. of Environmental Quality (www.lcd.state.or.us/tgm/publications.htm).
DfT (2009), Transport Analysis Guidance: 3.6.2: The Severance Sub-Objective, Department for Transport (www.dft.gov.uk); at www.dft.gov.uk/webtag/documents/expert/unit3.6.2.php.
Reid Ewing (1996), Best Development Practices; Doing the Right Thing and Making Money at the Same Time, Planners Press (www.planning.org).
FHWA (1987), Guidance for Preparing and Processing Environmental and Section 4(F) Documents, FHWA Technical Advisory T 6640.8A. Federal Highway Administration, U.S. Department of Transportation.
FHWA (1996), Community Impact Assessment: A Quick Reference for Transportation. Federal Highway Administration; at: www.ciatrans.net/TABLE.html. (See also the FHWA web site for more resources on Community Impact Assessment, available at: http://www.ciatrans.net/ciahome.shtml.)
FHWA (2010), Livability in Transportation Guidebook: Planning Approaches that Promote Livability, FHWA-HEP-10-028, Federal Highway Administration. USDOT (www.fhwa.dot.gov); at www.fhwa.dot.gov/livability/case_studies/guidebook.
David J. Forkenbrock and Glen E. Weisbrod (2001), Guidebook for Assessing the Social and Economic Effects of Transportation Projects, NCHRP Report 456, Transportation Research Board (www.trb.org); at http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_456-a.pdf.
HUD-DOT-EPA (2010), Interagency Partnership for Sustainable Communities, U.S. Housing and Urban Development, Department of Transportation and Environmental Protection Agency (www.epa.gov/dced/partnership/index.html).
LACDPH (2011), Model Design Manual for Living Streets, Los Angeles County Department of Public Health (www.modelstreetdesignmanual.com).
LCC (2008), Smart Growth Scorecard, Livable Communities Coalition (www.livablecommunitiescoalition.org); at www.livablecommunitiescoalition.org/uploads/100012_bodycontentfiles/100636.pdf.
FHWA Livability Initiate (www.fhwa.dot.gov/livability) is a website that describes how the U.S. Federal Highway Administration is supporting livability objectives.
Todd Litman (2002), “Evaluating Transportation Equity,” World Transport Policy & Practice (http://ecoplan.org/wtpp/wt_index.htm), Volume 8, No. 2, Summer, pp. 50-65; revised version at www.vtpi.org/equity.pdf.
Todd Litman (2006), Community Cohesion As A Transport Planning Objective, Paper 07-0550, Transportation Research Board 2007 Annual Meeting; at www.vtpi.org/cohesion.pdf.
Todd Litman (2009), Transportation Cost and Benefit Analysis, Victoria Transport Policy Institute (www.vtpi.org/tca).
NZTA (2010), Economic Evaluation Manual, Volumes 1 and 2, New Zealand Transport Agency (www.nzta.govt.nz); at www.nzta.govt.nz/resources/economic-evaluation-manual/volume-1/index.html and www.nzta.govt.nz/resources/economic-evaluation-manual/volume-2/docs/eem2-july-2010.pdf.
PPS (2008), Streets As Places: Using Streets To Rebuild Communities, Project for Public Spaces (www.pps.org); at www.pps.org/pdf/bookstore/Using_Streets_to_Rebuild_Communities.pdf.
PPS (2008), The Quiet Revolution in Transportation Planning: How Great Corridors Make Great Communities, Project for Public Spaces (www.pps.org); atwww.pps.org/pdf/bookstore/Great_Corridors_Great_Communities.pdf.
Rahman, O. M. A. "Visual Quality and Response Assessment: An Experimental Technique," Environment and Planning B, Vol. 19. 1992, pp. 689-708.
Shannon H. Rogers, John M. Halstead, Kevin H. Gardner and Cynthia H. Carlson (2010), “Examining Walkability And Social Capital As Indicators Of Quality Of Life At The Municipal And Neighborhood Scales,” Applied Research In Quality of Life (www.springerlink.com), DOI: 10.1007/s11482-010-9132-4; at www.springerlink.com/content/xtq06270p27r1v0h.
S. Ryan (1999), "Property Values and Transportation Facilities: Finding the Transportation-Land Use Connection," Journal of Planning Literature, Vol. 13, No. 4, May pp. 412-427.
Social Research in Transport (SORT) Clearinghouse (www.sortclearinghouse.info) is a repository of reports and links to research findings focused on social issues in transport.
Tri-Met (2002), Community Building Sourcebook, Tri-Met, Portland Oregon Transit Agency (www.trimet.org/inside/publications/sourcebook.htm).
WSDOT (2003), Building Projects that Build Communities: Recommended Best Practices, Community Partnership Forum, Washington State Department of Transportation (www.wsdot.wa.gov/ta/paandi/paihp.html).