The Nation’s transportation system accommodates extensive local and long- distance travel to meet the demands of more than 321 million U.S. residents and 75 million foreign visitors. In 2014 person-miles of travel (PMT) in the United States was roughly 5.4 trillion, nearly 70 percent of which was in cars or other personal vehicles, while domestic and international air travel to and from this country accounted for about 23 percent—with 11 percent domestic and 12 percent international (table 2-1).¹ Transit, intercity rail, and bus services accounted for the remaining PMT. Walking and biking also tallied a large number of local trips and travel-miles, with nearly 5 million people getting to work under their own power daily [USDOC CENSUS 2016a].

The number of commercial air passengers and airline revenue passenger-miles reached a new high in 2015, as discussed in the long- distance travel section, rebounding fully from sharp declines during and after the 2008 and 2009 economic recession. Highway PMT by cars and other personal vehicles in 2014 has rebounded somewhat but remains well below the peak set in 2007 prior to the recession.

Transit and intercity passenger rail services grew in number of passengers and passenger- miles during the recession and in most years thereafter.

Local Travel

As illustrated in table 2-2 and figure 2-1, local travel often involves repetitive daily trips (e.g., the daily commute to and from work or school). Social/recreational activities, family/ personal errands, and shopping accounted for nearly 60 percent of household travel and 70 percent of household trips. U.S. households averaged about 9.6 trips per day, with the average trip slightly under 10 miles in length in 2009 (table 2-2). Total travel per household was about 33,000 miles, or 13,200 miles per capita that year. These 2009 benchmarks are from the last National Household Transportation Survey (NHTS) [USDOT FHWA NHTS 2011].² The Federal Highway Administration’s new travel survey was underway in 2016.

Work commutes and work-related trips are typically longer than other types of local travel, making up about one-fourth of total mileage traveled but less than one-fifth of total trips. The shorter trips were typically for shopping, personal business, and social/recreation—each with greater shares of the number of trips but a lower share of PMT than the work commute (table 2-3).

Personal vehicles were used for 86 to 88 percent of journeys-to-work in the 2000 to 2014 period. However, driving alone continued to rise in share and numbers, while carpooling declined. Nearly 11 million more people drove alone to work in 2014 than in 2000, while the number of carpoolers fell by 2, as shown in figure 2-2. Transit ridership increased by over 1 million in the 15-year period, with transit’s share of commuters rising to 5.1 percent, up from 4.7 percent in 2000. About 517,000 more people walked or biked to work in 2014 than in 2000, accounting for about 3.3 percent (or 4.8 million) of all commuters in 2014.

The geography of commuting has changed:

• Workers live farther from their places of work than in earlier decades.
• Workers leaving their home county to work in another county increased from 23.5 million to 40.1 million between 1990 and 2014; their percentage share of the workforce grew from 20.4 to 27.5 percent.
• More people are working at home. Advanced communication and information technologies have increased the ability of people to work at home while performing their job responsibilities. Part of the longer term growth in working at home had been masked in earlier decades by the number of people who worked on the farm where they also lived [AASHTO 2013].

In 2014 about 4.5 percent of workers (or 6.2 million) worked primarily at home. The 2014 number does not count those who work one or two days per week at home, spending the other days at a job site. A 2010 Census survey found that 13.4 million people worked from home at least 1 day per week. Monday and Friday are the most likely days to telework and Thursday is the least likely³  [USDOC CENSUS 2013a].

The NHTS survey found that about one-fifth of trips involve trip-chaining in which people sandwich in daily errands and activities, such as dropping off and picking up children at school/day care or stopping at a fitness center, while on the way to and from work [USDOT FHWA NHTS 2011].

Figure 2-3 traces the average number of daily trips per person by major purposes as reported in the four national travel surveys completed since 1990. The number of work trips has been stable, but the share has declined relative to other trips as travel for other trip purposes increased.

The number of trips varies throughout the week (figure 2-4). Friday accounted for the most trips, because of more social/recreational and family/personal/errand trips, and Sunday for the least. Reduced numbers of work trips and errands on Saturday and Sunday are partially offset by shopping and social/ recreational trips, as well as travel to religious services.

As shown in figure 2-5, the overwhelming majority of person trips for all purposes are taken in cars or other personal vehicles. Walking is used for a substantial number of errands and social/recreational trips. Family/ personal errands and social/recreational activities accounted for more than two-thirds of trips, followed by trips to and from work, which accounted for 15.6 percent.

Supporting the high percentage of travel by personal vehicle, 9 out of 10 households have access to automobiles and other vehicles. The share of households without a vehicle declined from over 11.5 percent in 1990 to 8.7 percent in 2007. The most recent data indicate that roughly 10.7 million households, 9.1 percent of all households in 2014, did not have access to a vehicle. The number of households without vehicles has stayed about the same, at 10 to 11 million for several decades, despite a growing number of households [AASHTO 2013].

About 14.8 percent of workers with no available vehicle walked to work, roughly four times the percentage for workers with one available vehicle. Similarly, 2.8 percent of those without a vehicle biked to their workplace, compared with 0.8 percent for workers with one available vehicle. Specifically, households with no workers accounted for two-thirds of the households with no vehicles [USDOC CENSUS 2016a]. Only 4.5 percent of households with workers had no vehicle in 2014, but this represents 6 million workers [MCKENZIE 2015].

About 11.6 percent of households have more workers than vehicles. The other 88.4 percent are about evenly split (about 44 percent each) between households with more vehicles than workers and households where the number of vehicles equals the number of workers [AASHTO 2013].

National trends do not portray travel in individual metropolitan areas. For example, transit serves a higher share of work trips in larger metropolitan areas: 11.0 percent in areas with a population over 5 million, 4.0 percent in areas between 2.5 and 5 million, and 2.2 percent in areas between 1 and 2.5 million (figure 2-6). Transit ridership is highest in the New York-Newark-Jersey City, NY-NJ- PA; San Francisco-Oakland-Fremont, CA; Washington-Arlington-Alexandria, DC-VA- MD-WV; Boston-Cambridge-Quincy, MA- NH; Chicago-Naperville-Elgin, IL-IN-WI metropolitan areas.

Walking and Biking to Work

Nationally, only a small percentage of people walk or bike to work. However, these nonmotorized modes of commuting are important in many cities of all sizes, as shown by the 2008–2012 American Community Survey. In the 50 largest U.S. cities, 5.0 percent of workers walked to work and another 1.0 percent biked. Over 15 percent of workers in Boston, MA, walked to work, as did more than 10 percent of commuters in Washington, DC, Pittsburgh, PA, and New York City. Portland, OR (6.1 percent) and Minneapolis, MN (4.1 percent) had the highest percentage of bicycle commuters. These cities have also invested in infrastructure to facilitate biking (e.g., building dedicated bike lanes). Some small cities have higher rates of walking and biking, especially where colleges and universities are located. For example, about 42 percent of workers in Ithaca, NY, walk to work and nearly 19 percent in Davis, CA, commute by bike [MCKENZIE 2014].

Among regions, the Northeast has the highest rate of walking to work, while the West had the highest rate of biking. The South had the lowest rate of walking and bicycling to work for most city-size categories.

People walking or biking to work spend less time on their commute than those using other modes—walkers average 11.5 minutes and bikers 19.3 minutes, compared to 25.9 minutes for other modes. Women were slightly less likely to walk to work than men, but less than half as likely to commute by bike. People who walk or bike to work also tend to be younger than the average commuter. Many people walk or bike to work in part for the exercise it provides in contrast to less active means of commuting [MCKENZIE 2014].

Some people combine biking and transit to make their commutes and other trips. Box 2-A discusses bike-share programs, now common in many cities that offer expanded mobility options.

Long-Distance and International Travel

In many places the daily rhythms of local travel are affected by long-distance travel. Highway traffic between distant places contributes to local congestion on intercity highways. Traffic to and from airports also contributes to local congestion. Personal travel in recreational areas is dominated by seasonal variation (e.g., holidays, such as Memorial Day) as out-of-town visitors increase traffic counts along interstates that connect major cities and on local roads that lead to resort areas [DELDOT 2014].

Americans primarily use personal vehicles and airlines for their long-distance travel. There is no longer a comprehensive data source for long-distance travel (usually considered as trips to places at least 50 miles away). Although totals can be estimated from a variety of sources, the end result is incomplete—in terms of system usage for long-distance trips, trip purpose and length, and traveler characteristics. The missing pieces include trips by car or other personal motor vehicle (used by most people for their long- distance trips), general aviation, and cruise ships. Vehicle-miles of travel on rural interstate highways are occasionally used as a surrogate for long-distance highway travel, but there is no methodology for separating local from long- distance travel within rural areas. Takeoffs and landings of general aviation aircraft are not a good indicator because many flights take off and land at the same airport rather than carry people to distant destinations. Numbers of passengers boarding and debarking from cruise ships in each port are counted, but detailed statistics on cruises, cruise passengers, departure ports, and destination have not been compiled since June 2012.

Long-distance travelers include international visitors to the United States. Approximately 75 million foreign visitors came to the United States in 2014, an increase of 15 million from 2010. This was the fifth consecutive year of growth (figure 2-7). By contrast, in the 2000 to 2009 period, there were three consecutive years of declining numbers of foreign visitors after the September 2001 terrorist attacks and also a decline in 2009 during the global economic recession [USDOC OTTI 2015].

U.S. and foreign airlines carried 894 million passengers on domestic flights and international flights to and from the United States in 2015 (table 2-4). Passenger enplanements were up by about 44 million from 2014, the previous peak year. In 2015 domestic enplanements accounted for 78 percent of passengers, while international enplanements on U.S. and foreign airlines accounted for 22.0 percent [USDOT BTS OAI 2016]. U.S. airlines carried just over half (51.2 percent) of passengers traveling between the United States and international points.

Total (domestic and international flights in the United States) revenue passenger-miles also set all-time records in 2015, surpassing the previous record set in 2014, reaching nearly 1.3 trillion. Of this, international flights accounted for 51 percent of passenger-miles, the third year in a row that passenger-miles on these flights exceeded those on domestic flights [USDOT BTS 2016].

The number of domestic and international flights (9.5 million in both 2014 and 2015) has been trending downward since the peak of over 11.3 million flights in 2005, but these flights are carrying more passengers and have higher load factors than a decade ago. As shown in table 2-4, planes have become more crowded since 2005 as measured by load factors. Domestic flights were, in general, more crowded than international flights. Domestic flights in 2014 and also in 2015 accounted for roughly 85 percent of total U.S. flights, while international flights of U.S. and foreign carriers accounted for about 15 percent [USDOT BTS OAI 2015].

Long-distance railroad travel in the United States is primarily on Amtrak (also known as the National Rail Passenger Corp.). Amtrak ridership grew for 15 consecutive years between 1997 and 2012, rising from 19.7 million annual person-trips in its fiscal year 1997 to a peak of 31.2 million in 2012. While ridership has subsequently fallen a bit (to 30.8 million in 2015), ridership on its Northeast Corridor trains reached a record of 11.7 million in 2015 [AMTRAK 2015]. On the smaller Alaska Railroad, annual ridership peaked in 2007 at more than one-half million trips, and had not regained this level as of 2014. Customers traveling aboard railcars owned by cruise lines and pulled by the Alaska Railroad accounted for about half of the 2014 Alaska Railroad passengers [ARRC 2015].

Long-distance travel by motorcoach, including charter as well as scheduled service buses, declined somewhat in 2013 and 2014, compared to 2012 (table 2-5). There were about 604 million person trips in the United States and Canada in 2014, roughly 33 million fewer trips than in 2012 but slightly more than in 2010, when there were more carriers and coaches but fewer passenger trips per coach.

Just under half of all bus passengers in 2014 were either students or senior citizens [ABA 2016]. Charter service accounted for about 47.5 percent of motorcoach mileage, and scheduled service accounted for another 32.3 percent. The remaining miles were for commuting (4.6 percent); packaged tours (6.6 percent); transport to and from airports (3.7 percent); sightseeing (3.5 percent); and special operations, such as regular-route service to fairs, sports, and other events, and employee transport to work sites (1.8 percent).

Forces of Change in Travel

After decades of predictable growth, recent trends of U.S. travel behavior have become less clear. Many factors, such as the travel preferences of the aging baby boom generation,⁴ the younger millennial generation, the increasing popularity of shared mobility, the uncertainties about future levels of immigration, and the diminishing but possibly lingering effects of the economic recession spanning December 2007 to June 2009, affect local, long-distance, and international travel behavior.

Such factors have affected the demand for travel in the United States. Among the most important are population, employment, car ownership, household income, and economic conditions. The discussion below highlights some aspects of these factors.

Economics and Recession

U.S. gross domestic product (GDP) grew at about 3 percent per year in the early 2000s, but declined 0.3 percent in 2008 and 2.8 percent in 2009, before again growing each year from 2010 through the end of 2015.

Figure 2-8 charts GDP and highway vehicle- miles of travel (VMT) over the last 25 years, during which three recessions occurred. VMT⁵ remained stable or grew in the first two recessions, which were of relatively short duration and relatively mild. VMT shows a different pattern during the longer and more severe 2007–2009 recession. As the figure illustrates, VMT peaked in 2007, just as the recession began, then dropped in 2008 and 2009 and again in 2011 before beginning to rebound [USDOT FHWA 2015].

Airline travel was also adversely affected by the 2007–2009 economic recession. While the number of passengers on international flights to and from the United States returned to prerecession levels beginning in 2011, it was not until 2014 that enplanements on domestic flights finally exceeded their 2007 levels (figure 2-9). Only urban transit and intercity rail passenger volumes grew during and immediately after the recession (with the previously mentioned exception of the Alaska Railroad). Transit ridership was stimulated in part by rising gas prices in the 2002 to 2008 period (when average annual gas prices rose $1.91 per gallon nationwide) [USDOE EIA 2016].⁶ The recent decline in gas prices—a nationwide average decline of $1.19 per gallon between 2012 and 2015, with $0.91 of the decline occurring in 2015—raises the question of whether people who switched to transit when gas prices were high will go back to driving if gas prices remain low.

As shown in figure 2-10, person-miles of travel increase with household income. With the last national household travel survey completed in 2009, at the end of the recession, it remains to be seen what the next travel survey now underway will show about the trip-making propensities of the public.

Demographic and Geographic Shifts

Demographic factors underlie long-term travel demand. Between 1990 and 2015, the U.S. population grew by 70 million people, reaching 321 million, placing additional travel demands on the transportation system [USDOC CENSUS 2016b]. All census regions added population, but growth was not even across the country. More than 80 percent of the 1990 to 2015 population gain was in the South and West, continuing a decades- long trend [USDOC CENSUS 2001, 2011, and 2016]. About 60 percent of the Nation’s 3,143 counties, including nearly 80 percent of metropolitan counties, gained population from 2000 to 2015, with a total gain of about 42 million people. This contrasts with population losses of 2.7 million residents in the other 40 percent of counties [USDOC CENSUS 2016c, d]. These regional and metropolitan population changes affect transportation infrastructure needs and travel patterns.⁷

Demographic factors and the economy combine to affect travel demand through the growth of the labor force and the subsequent increase in journeys-to-work, and through growth in the income generated by the labor force, some of which is spent not only on essential travel, but also on discretionary trips. The number of people in the workforce increased by nearly 40 million, growing from about 119 million in 1990 to nearly 158 million in 2015 [USDOL BLS 2016].

Age is closely associated with the progression of the household life cycle (e.g., single person, married couple, households with small children and/or school age children, empty nesters, and retired individuals). Both the youngest (under 16 years of age) and the oldest (over 65 years of age) traveled the least compared to other age groups. The in-between age groups, particularly those between 36 and 65 years of age, accounted for the majority of person-miles traveled (PMT). This is a harbinger of future trends as older members of the labor force move toward the 65-year-age threshold where many people move into retirement.

As shown in figure 2-11, travel across all age groups (except those 16 years old and under) showed declines from 2001 to 2009. The youngest and oldest age cohorts seemed least affected by the December 2007 to June 2009 economic recession and its aftermath, while the working age groups were most affected, particularly those between 16 and 35 [NBER 2013]. Whether this is cyclical or a fundamental change in travel trends is not clear.

The baby boom generation, people born between mid-1946 and mid-1964, has generated much of the travel activity at the local and intercity level for many decades. Today, even as the trailing edge of the baby boom generation approaches early retirement age, boomers are still affecting travel patterns. They are the first generation in which both women and men have been close to reaching the saturation point in terms of driver licenses and vehicle availability. Thus, retired baby boomers could be expected to be more mobile in their retirement years than previous generations, as indicated by an increase in PMT among those aged 65 and older [AASHTO 2013].

The millennial generation, born after 1980, is often described as having very different attitudes toward location and transportation than their baby boomer parents. Millennials are described as less dependent on the automobile and more likely to live in central cities [SAKARIA STEHFEST 2013]. National data do not corroborate this description; among 16- to-24 year old members of the U.S. labor force who migrated between suburbs and principal cities, 250,000 left the suburbs for cities and 450,000 left the cities for suburbs, for a net loss of approximately 200,000 from 2011 to 2012 [AASHTO 2013]. Young people have been delaying the time when they acquire a driver’s license and purchase their first new car, but the delay may have far more to do with the economy and availability of jobs than with shifting preferences of today’s teenagers [AAA 2012]. Transportation as a share of spending is higher for people under the age of 35 than for any other age group [USDOL BLS 2012].

Time Spent Traveling

On weekdays in 2015, the average person spent 82.0 minutes per day traveling for a variety of activities. Examining the 44.7 percent of people who engaged in travel for work, the average person spent 46.7 minutes per day on this activity, the most for all activities.

On weekends and holidays, people spent an average of 85.9 minutes per day engaged in various travel activities, 3.9 minutes more than on weekdays. Out of all selected activities, the average person spent the most time (45.7 minutes) traveling for activities related to personal care, about 18.7 minutes per day more than on weekdays. Travel related to eating and drinking on weekends and holidays accounted for 33.3 minutes—about 8 minutes more than on weekdays [USDOL BLS 2016].

People spent less time traveling in 2015 than in 2003, according to the American Time Use Survey.⁸ On weekdays in 2015, people spent 4.8 fewer minutes traveling per day, a decrease of 5.6 percent from 2003. On weekends and holidays, people spent 4.5 fewer minutes traveling per day, a 5.0 percent decrease (figure 2-12).

Time spent traveling reached a low in 2014, falling below levels reached in the last recession. Due to a post-recession increase in weekday travel time combined with a continued decline in weekend travel time, average weekday and weekend/holiday travel time were almost equal in 2011. On average, people traveled nearly 4.0 minutes more on weekends and holidays than on weekdays.

Challenges for Travel

An important component of accessibility is having access to transportation options, in particular for those groups in society who have the most difficulty traveling or those who have limited access to transportation services. This section begins with a discussion of the degree of connectivity⁹ between public transportation modes, using data from the Bureau of Transportation Statistics’ (BTS’) Intermodal Passenger Connectivity Database. Other challenges discussed include access to transportation for people without a personal vehicle and transportation options for the elderly and for people with disabilities.

Passenger Access and Connectivity

People using public transportation (e.g., Amtrak, intercity bus, or commercial aviation) often need or wish to connect to another mode of transportation to reach their destinations. According to the 2009 National Household Travel Survey (NHTS), 99 percent of all transit trips used at least two transportation modes. Intermodal links between transportation modes (e.g., transit, intercity bus, or train station access at airports) give travelers more mobility options.

The BTS Intermodal Passenger Connectivity Database (IPCD) inventories the connectivity of passenger transportation facilities (e.g., air, long-distance bus and ferry, and intercity rail service), certain transit facilities (e.g., local ferry and heavy, light, and commuter rail), and bike-share. There are over 10,000 unique passenger travel facilities (figure 2-13), of which 44.4 percent do not offer connections to other transportation modes, 47.5 percent connect to one other mode, 8.1 percent connect to two other modes of transportation, and 0.1 percent connect to three other modes of transportation (e.g., bus, air, rail, ferry, or bike- share).

Specifically, 85.5 percent of the heavy rail- stations (high-speed transit rail on an exclusive right-of-way) offered connections to other modes and are the most connected of all travel options, followed by bike-share (with 74.8 percent), commuter rail (with 70.2 percent), light-rail transit (with 68.8 percent), and Amtrak/intercity rail (with 53.3 percent). About a quarter (23.7 percent) of airports with scheduled passenger service connect with other transportation modes. Only 12.2 percent of intercity bus facilities have connections to other modes (figure 2-13).

Bike-share systems that connect with other transportation modes extend the transportation network and increase modal options. A bike- share facility, for example, located within a block of a transit bus stop offers an alternative to taking transit and provides access to locations off the transit bus route. A total of 72 bike-share systems operate 3,923 stations in 125 U.S. cities as of October 2016 (figure 2-14).  Most bike-share docking stations (75.1 percent) can be found near local public transportation stops (transit bus, commuter rail, heavy rail, light rail, and/or transit ferry). Transit bus is the most typical connection, with 73.2 percent of bike-share stations located a block or less from a transit bus stop. [USDOT BTS 2016b]

Access to Transportation for People Without a Vehicle

Many people without access to a personal vehicle, especially people who are poor, have difficulty reaching stores, services, and workplaces outside of their immediate neighborhoods. As previously discussed, roughly 9 percent of households do not have access to a personal vehicle. In the most densely populated parts of cities (10,000 plus people per square mile), 28.4 percent of households had no vehicle in 2009 [USDOT FHWA NHTS 2011].

People living below the poverty level are less likely to own, or have access to, a personal vehicle to get to work than the population as a whole. Across the Nation the percentage of people in poverty increased from 12.2 to 14.8 percent between 2000 and 2014 as the number of poverty stricken persons increased from 33.3 million to 46.7 million¹⁰ [USDOC CENSUS 2013b, 2015]. BTS analysis of the 2009 NHTS found that households with annual incomes less than $25,000 were eight times more likely, on average, to be zero-vehicle households than households with annual incomes above that level [USDOT FHWA NHTS 2011]. Of workers below the poverty level, 64.3 percent drive to work compared to 76.8 percent of workers overall in 2014. Compared to commuters as a whole, people below the poverty level are more likely to carpool, take public transportation, walk, or use other transportation modes (compare in figure 2-15).

Transportation Access for Elderly and Disabled Passengers

Access to transportation options also is a challenge for many people who are elderly and for those with physical or cognitive impairments. The American Association of Retired Persons Public Policy Institute estimated that 12 percent of all trips and 10 percent of all miles traveled in the United States in 2009 were taken by persons age 65 and older [AARP 2011]. Transit use by people age 65 and older as a share of all the trips they took increased by 40 percent between 2001 and 2009, which represented more than 1 billion trips on public transportation in 2009 (a 55 percent increase from what was reported in 2001).

Over the last two decades, the Nation’s transit fleet has made notable progress in making transit service accessible to those with disabilities. Through the installation of lifts and ramps or improvements in station infrastructure, people using wheelchairs or who have other travel disabilities now find it easier to access transit than in the recent past. All but a few transit bus stations are now reported to be compliant with the Americans with Disabilities Act (ADA), the 1990 law that focused attention on transportation needs of people with disabilities, as are nearly all transit buses (at least among those services that report to the Federal Transit Administration). Almost all cars in the heavy rail transit fleet are now ADA complaint, but just 52.7 percent of heavy rail stations (like subway stations). Similarly, in the case of commuter rail, 87 percent of the train cars are compliant, but only 68.5 percent of the commuter rail stations. As for demand- response transit vehicles, where vehicles can be assigned based on a passenger’s individual needs, about 87 percent of the fleet is reported to be accessible [APTA no date, APTA 2016]. Box 2-B examines the interactions between transportation and public health.

After decades of predictable growth, recent indicators of U.S. travel have become less clear. Many factors, such as the travel predilections of the aging baby boom and the younger millennial generations, uncertainties about future levels of immigration, and the duration of continuing effects of the recent recession on travel, will enter into the equation. In order to understand possible changes in travel dynamics, good data about local, long-distance, and international travel will need to be collected on a regular basis. The central question for data development will be to distinguish what changes are cyclical phenomena, and therefore transient, from those that are structural and a fundamental part of a new era of travel behavior.

References

AAA Foundation for Traffic Safety (AAA). Timing of Driver’s License Acquisition and Reasons for Delay among Young People in the United States (2012). Available at http:// newsroom.aaa.com/ as of April 2016.

AARP Public Policy Institute (AARP). How the Travel Patterns of Older Adults Are Changing: Highlights from the 2009 National Household Travel Survey (April 2011). Fact Sheet 218. Available at http://www.aarp.org/ as of April 2016.

Alaska Railroad Corporation (ARRC). Business Facts: Alaska Railroad Passenger Services (January 7, 2016). Available at https:// www.alaskarailroad.com/ as of April 2016.

American Association of State Highway and Transportation Officials (AASHTO). Commuting in America 2013. Available http:// traveltrends.transportation.org/ as of April 2016.

American Bus Association (ABA) Foundation. 2016. Motorcoach Census 2014, (February 11, 2016). Available at http://www.buses.org/ as of April 2016.

American Journal of Public Health, Research and Practice (AJPH). Pucher, et al. “Walking and Cycling in the United States, 2001-2009: Evidence from the National Household Travel Surveys.” 2011. Supplement 1. V1. S1. 9-11

American Public Transportation Association.

—2016: 2016 Public Transportation Fact Book Appendix A: Historical Tables. April 2016. Available at https://www.apta.com/ as of May 2016.

—No date: ADA Facts at a Glance. No date. Available at https://www.apta.com/ as of May 2016.

Delaware Department of Transportation (DelDOT). Traffic Alert - DelDOT Urges Drivers To Slow Down This Holiday Weekend (May 20, 2014). Available at http://www. deldot.gov/ as of May 2015.

Firestine, Theresa, “Bike-Share Stations in the U.S.”, Technical Brief (April 2016). U.S. Department of Transportation, Bureau of Transportation Statistics. Washington, DC. Available at http://www.bts.gov/ as of April 2016.

Iseki, Hiroyuki; Ali, Rubaba (ISEKI; ALI). Net Effects of Gasoline Price Changes on Transit Ridership in U.S. Urban Areas. (December 2014). Available at http://transweb.sjsu.edu/ as of April 2016.

Mckenzie, Brian (MCKENZIE):

—2014: “Modes Less Traveled: Commuting by Bicycle and Walking in the United States 2008-2012.” American Community Survey Reports, ACS-26. U.S. Census Bureau. Washington, DC. Available at https://www. census.gov/ as of April 2016.

—2015: “Who Drives to Work? Commuting by Automobile in the United States: 2013.” American Community Survey Reports, ACS- 32. U.S. Census Bureau. Washington, DC. Available at https://www.census.gov/ as of April 2016.

National Bureau of Economic Research (NBER). U.S. Business Cycle Expansions and Contractions. Available at http://www.nber.org/ as of May 2015.

National Railroad Passenger Corporation (AMTRAK). Amtrak Ridership And Ticket Revenue Steady In Fiscal Year 2015. (December 2, 2015). Available at http://www. amtrak.com/ as of April, 2016.

Sakaria, Neela; Natalie Stehfest. Millennials & Mobility: Understanding the Millennial Mindset and New Opportunities for Transit Providers (July 2013). Transit Cooperative Research Program (TCRP) 61. Available at http://onlinepubs.trb.org/ as of April 2016.

U.S. Department of Commerce (USDOC), Census Bureau (CENSUS):

—2016a: American Community Survey (ACS). Commuting. S0801. Available at http://www. census.gov/ as of April 2016.

—2016b: Annual Estimates of the Resident Population: April 1, 2010 to July 1, 2015. . Available at http://factfinder2.census.gov/ as of April 2016.

—2016c: Cumulative estimates of Resident Population Changes for Counties and County Rankings: April 1, 2010 to July 1, 2015. Available at http://www.census.gov/ as of May 2016.

—2016d: Metropolitan and Micropolitan Main. Available at http://www.census.gov/ as of May 2016.

—2014: Poverty: 2012 and 2013. American Community Survey Brief. Available at http:// www.census.gov/ as of April 2016.

—2013a: Working at Home is on the Rise. Available at http://www.census.gov/ as of April 2016.

—2013b: Poverty: 2000 to 2012. American Community Survey Brief. Available at https:// www.census.gov/ as of April 2015.

—2012: American Community Survey (ACS). DPO3. Available at http://www.census.gov/ as of April 2016.

—2011: Population Distribution and Change: 2000 to 2010. 2010 Census Brief. C2010BR-01. Available at http://www.census. gov/ as of April 2016.

—2001: Population Change and Distribution: 1990 to 2000. 2000 Census Brief. C2KBR/01-2. Available at http://www.census. gov/ as of April 2016.

U.S. Department of Commerce (USDOC), Bureau of Economic Analysis (BEA), Monthly Disposable Income, Personal Consumption Expenditures and Personal Saving (December 2013). Available at http://www.bea.gov/ as June 2015.

U.S. Department of Commerce (USDOC), Office of Travel and Tourism Industries (OTTI), Monthly Tourism Statistics (1996- 2014). Available at http://travel.trade.gov/ as of May 2015.

U.S. Department of Energy (USDOE), Energy Information Administration (EIA). 2016. Average Annual Gasoline Pump Price, 1929 — 2015, Fact of the Week #915. Available at http://eia.gov as of April 2016.

U.S. Department of Labor (USDOL). Bureau of Labor Statistics (BLS):

—2016a. Labor Force Statistics from the Current Population Survey. Series ID LNS12000000. Available at http://www.bls. gov/ as of September 2016.

—2015b. American time use survey—2014 results. (June 24, 2015). USDL-15-1236. Available at http://www.bls.gov/tus as of April 2016.

—2016. American Time Use Survey 2015, available at www.bls.gov as of October 2016.

—2012. Consumer Expenditure Survey (CEX). CE Database (2012). Available at http://www. bls.gov/ as of June 2015.

U.S. Department of Transportation (USDOT). DOT Releases New Online Tool to Help Promote Health through Transportation (November 3, 2016). Press notice available at www.transportation.gov as of April 2016; Online tool is available at www.transportation. gov as of April 2016.

U.S. Department of Transportation (USDOT). Bureau of Transportation Statistics (BTS):

—2016a. 2015 Annual and December U.S. Airline Traffic Data. BTS 15-16, March 10. Available at http://www.bts.gov/ as of April 2016

—2016b. Intermodal Passenger Connectivity Database (IPCD). Available at http://www.bts. gov/ as of April 2016.

—National Transportation Statistics (NTS). Available at http://www.bts.gov/ as of April

 —Office of Airline Information (OAI). T-100 Segment Data. Available at http://www.bts. gov/ as of April 2016.

U.S. Department of Transportation (USDOT). Federal Highway Administration (FHWA).

—2016. Traffic Volume Trends: December 2015. Available at http://www.fhwa.dot.gov/ as of April 2016.

—2011. National Household Travel Survey (NHTS) 2009 (June 2011). Available at http:// nhts.ornl.gov/ as of April 2016.

U.S. Department of Transportation (USDOT), Federal Transit Administration (FTA). 2014 National Transit Summaries and Trends— Report Year 2014. Appendix A. February 2015. Available at http://www.ntdprogram.gov/ as of April 2016.

U.S. Environmental Protection Agency (USEPA), Lead Trends. Available at http:// www.epa.gov/ as of April 2016.

World Bank. Phasing Out Lead from Gasoline: Worldwide Experiences and Policy Implications. Technical Paper 397 (1998). Available at http://siteresources.worldbank.org/ as of April 2016.

¹ Previous editions of this annual report only included domestic flights in annual PMT counts and did not in- clude air travel to and from the United States.

² The National Household Transportation Survey (NHTS) or similar national surveys have been conducted every 8 to 10 years since 1969.

³ The findings of the two Census Bureau surveys are not comparable because, among other matters, they use differ- ent definitions. The 2014 estimate is from the American Community Survey and the 2010 estimates are from the Survey of Income and Program Participation. Yet another survey, the American Time Use Survey, conducted by the U.S. Bureau of Labor Statistics, found that 23 percent of employed persons did some or all of their work at home, and 85 percent did some or all of their work at their work- place in 2014 [USDOL BLS 2015b].

⁴ In a formal demographic sense, people born from mid- 1946 to mid-1964, but more generally, people born in the post-World War II period.

⁵ Vehicle-miles of travel, or VMT, is a key measure of travel activity that is used, among other things, to estimate person-miles of travel, or PMT. VMT is multiplied by estimates of vehicle occupancy to measure PMT. Because the national vehicle occupancy rates used to estimate PMT were last estimated in the 2009 NHTS, there is more uncertainty surrounding estimates of PMT than of VMT.

⁶ A 2014 report, Net Effects of Gasoline Price Changes on Transit Ridership in U.S. Urban Areas, examines the impact of gasoline price increases on transit ridership in 10 U.S. urbanized areas [ISEKI; ALI 2014]. The report is discussed in Transportation Statistics Annual Report 2015, chapter 2

⁷ For a more detailed discussion of demographic trends and travel from 1950 forward, see Transportation Statis- tics Annual Report 2013, pages 56–58.

⁸ The time use survey asks individuals to identify how they spent their time on certain days. The survey results should not be compared to results from other measure- ment instruments, such as congestion indices based on vehicle time/distance estimates discussed in chapter 4.

⁹ Connectivity puts travelers in closer proximity to ad- ditional transportation alternatives that unconnected, parallel systems do not offer.

¹⁰ There is no statistically significant difference in the poverty rate between 2011 and 2014, while the poverty rate increased each year in the four years prior to 2011.