Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
16 CHAPTER 2. UNDERSTANDING THE ROLE OF DISTANCE IN CHOICE OF MODE 2(A) UNDERSTANDING THE RELATIONSHIP BETWEEN DISTANCE AND MODE Chapter 2 of the Technical Appendix now introduces a central concept in this ACRP project-- the key role played by the factor of distance, the most basic causal factor involved in the decision between the car and airplane. This chapter presents a summary of known information about the role of trip distance, which was highly influential in both the design of the 2017 ACRP Survey, and the design of the research described later in this document, where the results of the new survey are examined primarily in terms of the interaction between trip distance and wide variety of additional explanatory factors. LOOKING AT DISTANCE The length of the trip is a major variable in the examination of the competition between air travel and travel via automobile. Most long-distance travel occurs in the shorter trip lengthsâfor example, 85% of long-distance trips by all modes of travel and for all purposes are between 100 miles and 800 miles one way. Figure 2-1 was created as part of the model development process for FHWAâs Fundamental Knowledge project. (The red âModel Proportionâ bars are not important to the current analysis as these do not vary much from the empirical data presented as âDB1B proportion.â) Figure 2-1 illustrates that approximately 40% of air trips in the United States are under 800 miles, with most air trips under 1,100 miles from the county of trip origin to the county of trip destination. No distance category in Figure 2-1 over 2,600 miles accounts for more than 1% of total trips, even though the air trip database used here includes zones in Alaska and Hawaii. (Air trips included in this database for Alaska represent less than 1%, with trips for Hawaii representing approximately 2%.) For scale, a trip from Miami to Seattle is approximately 2,700 miles using Great Circle Route calculations.
17 FIGURE 2-1: DISTRIBUTION OF AIR TRIPS BY ORIGIN-TO-DESTINATION DISTANCE Source: Federal Highway Administrationâs TAF Multimodal Interregional Passenger Travel Origin Destination Data project. MODE SHARE, BY DISTANCEâAMERICAN TRAVEL SURVEY (ATS) DATA FROM 1995 Figure 2-2 uses ATS data (1995)âbased on earlier analysis for the FHWAâto illustrate how the role of air increases in concert with trip distance and, inversely, how the role of automobile decreases with the rise in trip distance. In the1995 survey, the automobile dominated for trips under 600 miles, at which point air dominated for longer trip lengths. Air mode share climbs over 10% at the 200-mile trip distance. Automobile mode shares of approximately 20% persist until 1,500 miles, falling to under 10% only for trips over 1,500 miles, based on 1995 data.
18 FIGURE 2-2: MODE SHARES, BY DISTANCE (1995) Source: McGuckin from American Travel Survey, 1995 data THE IMPACT OF INCOME ON MODE SHARE, BY TRIP DISTANCE These highly aggregated travel statistics can be analyzed along several dimensions. First, the role of income is critical in the decision-making for travel mode. Using the 1995 ATS dataset, the research team contrasted the travel for leisure activities of those from households making more than $100,000 with those from households making less than $25,000. Figure 2-3 shows the dramatic effect of the choice of air versus automobile as a function of trip distance for both income groups. There is little difference between the mode choice of the two groups for trips under 400 miles, with the automobile holding nearly 90% of the market. The difference between the two income groups widens until trips of approximately 900 miles, at which point the lower- income group airplane choice also increases. 0 10 20 30 40 50 60 70 80 90 100 M od eÂ sh ar eÂ of Â Lo ng âD ist an ce Â P er so nÂ Tr ip s ModeÂ ShareÂ asÂ aÂ FunctionÂ ofÂ TripÂ LengthÂ POV Air Train,Â BusÂ andÂ Other
19 FIGURE 2-3: EFFECT OF INCOME ON THE AUTOMOBILE SHARE OF TRAVEL FOR LEISURE, BY TRIP DISTANCE (1995) Source: McGuckin from American Travel Survey THE IMPACT OF PARTY SIZE AND INCOME ON MODE SHARE, BY DISTANCE Figure 2-3 illustrates the interaction between trip distance and income in the choice of mode for leisure travel, but additional variables affect the determination of mode share. For example, Figure 2-4 shows travel for all purposes and the mode share by income category and travel party size. In this chart, individuals traveling alone are depicted using solid lines, and individuals traveling in groups of two or more are depicted using dotted lines. Perhaps most dramatic is the comparison of the lower-income group in the multiparty trip with the higher-income group with the single-party trip. Most of the upper-income, single-party trip-makers have abandoned the automobile for the airplane for trips as short as 300 miles; most lower-income, multiparty trip- makers do not reach this level of mode share until trips exceed 1,000 miles. The general slope of the curves for the two âmiddle groupsâ is quite similar for lower-income traveling alone and upper-income traveling in a group. 0 10 20 30 40 50 60 70 80 90 100 Less than 200 200 - 299 300 - 399 400 - 499 500 - 599 600 - 699 700 - 799 800 - 899 900 - 999 1,000 or more Pe rc en t o f T rip s One Way Trip Distance in Miles $100,000 or more Less than $25,000
20 FIGURE 2-4: THE EFFECT OF INCOME AND PARTY SIZE ON AUTOMOBILE SHARE, BY DISTANCE (1995) Source: McGuckin from American Travel Survey. THE IMPACT OF TRIP PURPOSE ON MODE SHARE, BY DISTANCE Trip purpose is an important determinant for mode choice. The research team selected the Chicago area as a representative area to examine the impact of trip purpose on mode share, by distance. Both Washington, DCâwith a lower use of the automobile, and Denverâwith higher use of the automobileâwere examined by the research team to identify regional differences in mode share, by trip distance. Figure 2-5 shows the growth of the air mode with an increase in trip distance, as anticipated based on previous research. In other words, the air choice curve for business trips is much sharper than nonbusiness trips as distance increases. More important are the comparative mode shares within a given distance category. In the 200-mile to 400-mile distance band, the air share for nonbusiness trips is approximately one-third the share of business trips. By the distance band of over 1,000 miles, nonbusiness trip air shares are four-fifths the business trip shares. In effect, the choice of air for nonbusiness trips matches business trips as trip distance increases. Figure 2-5 is based on data collected for FHWAâs Foundational Knowledge project, which is described in Chapters 4 and 5 of this Appendix. That data was organized within the ârjourneyâ database, which is the source for the following charts. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 100â199 200â299 300â399 400â499 500â599 600â699 700â799 800â899 900â999 1000Â and more SingleÂ TravelerÂ LowÂ IncÂ (<$30K) SingleÂ TravelerÂ HighÂ IncÂ (>$100K) TwoÂ orÂ MoreÂ LowÂ IncÂ (<$30K) TwoÂ orÂ MoreÂ HighÂ IncÂ (>$100K)
21 FIGURE 2-5: EFFECT OF TRIP PURPOSE ON AIR SHARE, BY TRIP DISTANCE Source: rJourney output. VARIATION IN MODE SHARE, BY REGION AND TRIP PURPOSE The research team explored the difference between automobile and air travel behavior for four regions. Figure 2-6 illustrates that trip-makers in the Mountain States choose the automobile for long-distance travel at a rate significantly higher than trip-makers located farther east. There is also an absence of variation in automobile choice among/between Chicago, Illinois; Washington, DC; and Boston, Massachusetts. FIGURE 2-6: MODE SHARE TO AUTOMOBILE FOR FOUR REGIONS (NONBUSINESS, OVER 1,000 MILES) Source: rJourney database. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 100-200 200-350 350-500 500-1 K Over 1K Trip Distance in Miles Business Purpose Non-business 0% 5% 10% 15% 20% 25% 30% Denver Chicago Wash DC Boston
22 The research team compared the impact of distance in the eastern United States to the Mountain States by using Washington, DC, as an example for the eastern region. Figure 2-7 shows that the difference between the two regions in their propensity to choose the automobile occurs most strongly for trips between 200 miles and 500 miles. By contrast, the choice of the automobile for business trips longer than 1,000 miles and less than 200 miles is less influenced by location than for mid-distance trip-making. FIGURE 2-7: EFFECT OF DISTANCE ON MODE SHARE, DENVER VS. DC FOR BUSINESS TRIP PURPOSE Source: rJourney database. The automobile gains a greater share of nonbusiness trips than business trips, as shown in Figure 2-7 and Figure 2-8. For example, the nonbusiness travelers (Figure 2-6) in Washington, DC, exhibit less of shift away from the automobile for trips between 200 and 500 miles than business travelers (Figure 2-7). In effect, the Washington, DC, group behaved more like the Denver, Colorado, group on nonbusiness trips than on business trips. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 100-200 200-350 350-500 500-1 K Over 1K Trip Distance in Miles Denver WashDC Linear (Denver) Linear (WashDC)
23 FIGURE 2-8: EFFECT OF DISTANCE ON MODE SHARE, DENVER VS. DC FOR THE NONBUSINESS TRIP Source: rJourney database. For the longest trips, a higher proportion of nonbusiness trip-makers than business trip-makers travel via automobile. In every trip distance category, automobile use was higher for the Denver, Colorado, group than for the Washington, DC, group. 2(B) HISTORICAL TRENDS IN MODE SHARE, BY DISTANCE MODE, BY DISTANCE (1995 VS. 2002) Changes in the Role of Air and Automobile by 2002 National long-distance data that systematically includes travel by both automobile and air is provided in only two surveys: the ATS of 1995 and the National Household Travel Survey (NHTS) of 2001. The latter attempted to monitor both local and long-distance trips in one survey. An early review of the 1995 and 2001 data (partly collected in the winter of 2001 and in 2002) suggests that the role of the automobile in trips under 1,000 miles was significantly higher in the difficult period after the events of 9-11. The research team compared air/automobile mode shares in the 1995 survey to those in the (smaller) 2002 survey. Accepting her caution that the two surveys are not perfectly parallel, the results still suggest that the relative role of the auto in the lower end of the long-distance trip distance range was growing compared to the 1995 base year. The extent to which that increased role reflected only the peculiar conditions of that time period remains the subject for further research. Chapter 8 of this Technical Appendix documents the evident implications of the 2017 ACRP Survey results â which tend to confirm the hypothesis of increased auto reliance, but not to the degree implied in the 2001-2002 data collection period. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 100-200 200-350 350-500 500-1 K Over 1K Trip Distance in Miles Denver WashDC Linear (Denver) Linear (WashDC)
24 Figure 2-9 (lower, orange line) shows that in 1995, trips around 900 miles had an automobile mode share of 40% of the air and automobile market. The 2002 data (higher, blue line), however, shows automobile with somewhere near 70% of the same market; this period included a de- emphasis of the legacy carriersâ hub and spoke system and the initial introduction of additional security processing time at airports across the United States. This general pattern is consistent with a decade-long pattern of change of services provided by the airline sector, whose relative decrease in short-distance flights between 2007 and 2012 was illustrated earlier, in Figure 1-8. FIGURE 2-9: AUTOMOBILE SHARE OF LONG-DISTANCE TRAVEL (1995 VS. 2002) Source: McGuckin from American Travel Survey (1995) and National Household Travel Survey (2002). ESTIMATED MODE, BY DISTANCE (1995 VS. 2012) As demonstrated earlier in Figure 1-7, the airline industry did bounce back from the short-term impacts of 2001 and 2002. Figure 2-10 compares three categories of trip distance for ATS data in 1995 and FHWAâs estimated trip table data for 2012 to examine more recent efforts to document these changes.
25 FIGURE 2-10: ESTIMATED AIR MODE SHARE, BY DISTANCE (1995 VS. 2008) Source: ATS (1995); Source for 2008: FHWA, Developing Refined Estimates of Intercity Bus Ridership, 2016, page 14. These newer estimates suggest that the fall in mode share by air between 1995 and 2012 occurred primarily for trips under 1,000 miles, and not for longer trips, which is consistent with patterns observed elsewhere in this report. These recent estimates suggest that the growth in automobile mode share has been primarily occurred in trips under 1,000 miles. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Short, 500 -1000 Medium, 1000 -2000 Long, 2000+ 1995 Air Share 2008 Air Share