Transportation Impacts

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By definition, any proposed transit project will potentially influence elements of the local transportation system, including transit facilities and services, road traffic patterns and volumes, and parking. As such, environmental documents for transit projects should include a discussion of potential transportation impacts. The magnitude of these impacts will vary considerably depending on the scale and type of project a new fixed guideway project will have more impacts while construction of a bus storage facility may have little or none. Transportation impacts are divided into three categories, transit, traffic and parking, although additional transportation network impacts may occur, such as to air, freight, or other type of travel, if the project is intermodal. 


Construction of new transit facilities and/or expansion of transit services can affect existing transit operations. Potential impacts on transit systems should be analyzed and discussed in the environmental documentation for projects, although the level of analysis depends more on the magnitude and scale of the project than on the type of environmental document that is required. Specific transit considerations include: 1) changes in geographic areas of service; 2) travel times and reliability; 3) frequency and hours of service; 4) changes in transit patronage and demand; 5) changes in transit mode; 6) changes in station access and circulation; and 7) increased traffic around stations and depots.


Transit projects often cause changes in road traffic volumes, distribution and local circulation patterns, and must be considered during the environmental documentation process. The required level of analysis depends on the nature of project impacts rather than the type of environmental document being prepared. Low impact projects may simply require documentation that streets in the immediate vicinity of the project have sufficient capacity to absorb any anticipated additional traffic. High impact projects may require detailed analysis of anticipated changes to traffic throughout entire transportation corridors. In general, transit project sponsors should consult with FTA and city, county and/or state traffic engineering and planning officials as early as possible to identify potential traffic impacts and determine the level of analysis that will be needed in the environmental documentation.


Transit projects can affect the availability and location of parking spaces, and, although not often a significant impact, it can be a local concern. Potential parking impacts include externalities from new parking lots constructed to serve transit facilities, changes in parking demand as a result of transit facility construction/service expansion, and removal of existing parking spaces. Environmental documentation for transit projects should identify anticipated parking impacts and provide ways to avoid, minimize, and mitigate any adverse effects on nearby residential or business communities.

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