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18 transit agencies can take some steps on their own, and can New Bus Transit Systems initiate some strategies with the help of partners, to increase Comprehensive Service Expansion ridership and reduce GHG emissions. New Coverage in Urban Areas New Suburban Connections New Circulator/Distributor Routes EXPANDING TRANSIT SERVICE New Feeder Routes New Routes Connecting Disadvantaged Neighborhoods Expanding transit service, or increasing the supply of pub- to Jobs lic transportation, allows more people to use transit for a greater number of miles traveled. Agencies can expand tran- Based on a sample of empirical studies, the report found sit service by increasing the geographic coverage of routes, that ridership on most systems will increase by between 0.6% increasing service frequencies, extending operating hours, and 1% for every 1% increase in bus miles or bus hours oper- and adding new transportation modes. Adding route miles ated. Some studies show response rates well outside of this might include establishing new modes of public transporta- band. These figures suggest that passenger load factors fall tion within a given area, such as light rail transit (LRT) or on average as service increases, but results will vary from bus rapid transit (BRT), that provide higher quality service agency to agency and depend on the time scale of analysis. than the traditional bus services that account for the majority In general, ridership increases tend to be greater on systems of transit in the United States. with below-average service levels (20 ). To reduce GHG emissions, expanded transit service must A 2007 study by ICF International found that approxi- achieve some minimum vehicle occupancy rate. The net mately 51% of American households in 2001 had access to impact of each individual strategy on an agency's GHG emis- transit within 0.75 mi of their home. A household within this sions depends on the balance of new ridership and tailpipe band tends to drive 11.3 mi less each day than an identical emissions from additional transit vehicles. Agencies should household outside the band. That study found that, between consider both factors in planning any expansion strategies to 1999 and 2004, two-thirds of the ridership increase on U.S. reduce GHG emissions. transit services came from new route miles. The remaining one-third came from increased ridership on existing route Expanding Route Coverage miles. If transit agencies added 11,700 bidirectional route miles of rail transit and bus transit, the proportion of house- Expanding the coverage of transit routes both increases holds within 0.75 mi of transit would increase to 64%, and the number of people who can access transit and reduces public transit ridership would approximately double. As average times to access transit. The proximity of transit of 2007, about 3,858 route miles of rail service were at the service is a major factor determining Americans' use of stage of engineering, construction, planning, or proposal. public transit. Statistical analyses show, for example, that The equivalent amount of high-quality bus route miles was the density of rail service in a given area is positively cor- unknown (21). related with the distance traveled by public transportation (17 ). The distance from a person's home to the nearest tran- Increasing Service Frequency sit stop is particularly influential. A number of studies have found that people's willingness to walk to a bus stop drops Increased frequency of service can attract more riders to off dramatically at distances greater than one-quarter mile. existing transit route miles. More frequent service reduces People may travel several miles by bicycle to access tran- the average time that passengers spend waiting at stations sit (18 ). Expanding the number of households within these and bus stops, thereby reducing the total time needed for transit-accessible boundaries encourages more households travel, reducing the time that passengers may have to spend to use transit. in inclement weather conditions, and reducing the need to plan around infrequent service schedules. The EPA COMMUTER model estimates changes in tran- sit mode share based on variables including the proximity of Frequency of public transportation has a measurable impact transit. The model draws on empirical studies in a number of on ridership. A 2004 study found that the share of trips made U.S. urban areas. Depending on the specific urban area, the by automobile decreases significantly as service frequency at model predicts that the mode share of transit will increase the nearest bus stop increases (22). A separate TCRP study by between 0.02% and 0.09% for every 1 min decrease in found that for a 1% increase in bus service frequency (or average walk time to transit (19). decrease in headway), ridership increases between 0.3% and 1%, with an average of 0.5%. For a 1% increase in train ser- A TCRP report examined the impact of expanded cover- vice frequency (or decrease in headway), ridership increases age of bus service on ridership. Specific types of expansion between 0.08% and 0.9%. These figures indicate that passen- include the following: ger load factors are likely to fall as frequency increases, but