Chapter II. The Travel of Teens and Young Adults: State of the Literature
As we mentioned above, research on teenagers and travel behavior is limited—and research on young adults and travel behavior is nearly non-existent. In our literature scan, we identified fewer than 50 articles on the topic; moreover, many of the studies come from a small group of authors writing about a limited number of topics.3 The vast majority of research in the field has been conducted in the last decade, with only a handful of studies occurring earlier.4 Most of this research focuses on teenagers in the United States, although a few studies examine teenagers in Canada, Australia, and Great Britain. Research on young adults and travel behavior is even more limited, with only a handful of studies focusing on this age group specifically.
The literature we examine only includes studies that examine travel behavior and demographics in some fashion; it excludes a much larger body of work examining teenage travel exclusively in terms of accident rates. For example, many authors have examined the effect of graduated drivers’ license programs on teenager crash and fatality rates (e.g., Williams and Ferguson, 2002; Shope, 2007); these studies consistently demonstrate that such programs reduce crashes (Shope, 2007). However, few of the studies have analyzed the effects of graduated driver’s licensing programs in terms of mode choice or trip-making—for example, whether the laws cause teenagers to travel less overall or substitute transit trips for automobile trips.
While researchers in the fields of engineering and urban planning are the main producers of youth travel behavior studies, a look at the publications citing this literature suggests that researchers in public health departments are currently the main consumers of the research. For example, references to youth travel behavior studies appear frequently in articles exploring the linkages between physical activity—or lack thereof—and childhood and adolescent obesity.5
Six major themes appear in the research on youth and travel behavior:
- Descriptive data on travel patterns;
- Travel to and from school;
- Alternative modes of travel (i.e., not single-occupant vehicle travel);
- The relationship between travel and urban form;
- Travel behavior differences by gender; and
While these six themes are distinct, many of the articles included in our review cover more than one theme. For example, articles focusing on travel to school frequently mention safety issues for children traveling via alternative modes. We describe each of these themes in turn below.
A. Descriptive Data
As the name implies, these studies offer general, descriptive statistics on teenagers’ mode choice and trip characteristics. These studies clearly demonstrate that teenagers use cars for the majority of their trips—whether they drive the cars themselves or someone else drives them.
The 2001 NHTS is the most-cited source for information on youth and travel behavior. According to the NHTS, children under 18 years in the United States make 3.5 trips on average per day—slightly less than the 4.3 daily trips adults make (McDonald, 2006). As with adults, children make the majority of their trips by automobile, but not to the degree that adults do (McDonald 2006). Summarizing previous studies, Copperman and Bhatt (2011) find that youth make roughly 65–70 percent of their trips by car, 12–16 percent of their trips by walking, and smaller shares by school bus, bicycle, and public transit.6 As one might expect, teenagers tend to abandon alternative modes of travel as soon as they can drive automobiles (Clifton, 2003). Automobile access quickly follows for teenagers who obtain a license: 40 percent of 16-year-olds in the 2001 NHTS reported having primary access to a vehicle (McDonald, 2006). Teenagers 16–18 years old drive themselves for nearly half their trips, with walking and transit trips declining correspondingly with age (Clifton, 2003; McDonald, 2006). Younger teenagers, who lack licenses, use alternative modes of transportation more than older teenagers, and have slightly lower trip rates as well (Clifton, 2003; McDonald, 2006).
At the same time, however, decreases in licensing rates do not necessarily correspond with decreases in automobile travel. Marzoughi (2011) analyzes travel data in Toronto, where only 38 percent of 16- to 19-year-olds have a driver’s license. Although solo driving rates have declined for teenagers—a trend correlated with a decline in driver’s license rates for teens—automobile passenger travel among teens has increased so that, in net, overall personal automobile travel has actually increased.
B. Travel to and from School
Travel to school is the most common trip purpose for children aged 0–18—at least on school days. On those days, travel to school accounts for over a third of total trips (McDonald, 2006). While a subset of studies focuses on teenagers’ travel to and from school, they are usually in the context of analyses of children’s overall school travel. Cars remain the most important mode of travel, accounting for 54 percent of all children’s trips to school, but buses and walking are also important modes, accounting for 30 and 15 percent of school trips, respectively (McDonald, 2006; Copperman and Bhatt, 2011). Walking was once a very important mode for travel to school, but its share of trips has dropped dramatically in the past few decades—from 40 percent in 1970 to 15 percent in 2000 (McDonald, 2007). This downward trend has prompted efforts in communities around the country to encourage more walking through Safe Routes to School programs (Hubsmith, 2006).
Trip distance affects mode choice greatly: for trips to school under a mile, walking accounts for 40 percent of trips—again, down from 90 percent in 1970 (McDonald, 2007). Gender and race, meanwhile, do not appear to have large effects on children’s mode choice when they travel to school (McDonald 2008). At the same time, however, Emond and Handy (2012) do find that female high school students are less likely than are their male counterparts to bike to school, though only a small number of high school students use bicycles at all.7 Finally, unlike their trip-chaining parents who tend to make stops on their way to and from work, children generally travel directly to school and about three-fourths of children go directly home after school (Clifton, 2003; McDonald, 2005; Copperman and Bhatt, 2011). However, over half of those children make additional trips after returning home.
C. Alternative Modes of Travel
While most teens drive, and the vast majority of teen trips are in private vehicles as either drivers or passengers, most research on teen travel mode has focused on alternative, non-automobile modes of travel. A number of these studies focus on walking and cycling. Examining African-American high school students in Baltimore, Voorhees et al. (2011) find that built environment factors and self-efficacy affected physical activity and walking. Emond and Handy (2012), surveying high school students in Davis, California, find that comfort with bicycling and perceived distance affect teenager’s decisions to cycle, echoing the finding in Voorhees et al. (2011) about self-efficacy. Parents’ attitudes and behavior also play an important role: teenagers are less likely to bicycle if their parents readily offer rides (Emond and Handy, 2012).
A few other studies have examined transit use. For example, one study of a yearlong program giving free bus passes to low-income teenage students in San Francisco found that bus passes increased both transit use and participation in after-school activities, although they did not increase school attendance as the program administrators had intended (McDonald et al., 2004).
D. Urban Form and Travel Behavior
Some researchers have attempted to examine the effects of urban form on travel behavior for teenagers. For example, Trowbridge and McDonald (2008), perhaps unsurprisingly, find that teenagers in sprawling areas are more likely to drive than teenagers who live in denser areas. McMillan (2007), examining density and other urban form variables on youth travel, finds that urban form has a small but significant effect on travel behavior. That effect, however, applies more to children in high-income and white households than to children in low-income and minority neighborhoods (McMillan, 2007). Dalton et al. (2011) examine more specific urban form factors influencing rural teenagers’ travel to and from school. They find that the teenagers were more likely to walk or bicycle in neighborhoods with many intersections, places to eat, and tall buildings close to the streets—all of which correspond to higher-density areas.
E. Gender Differences in Travel Behavior
General research on women’s travel behavior shows a clear difference between women and men. Likewise, several researchers have discovered important differences between teenage girls and boys. In urban areas, teenage women travel in cars for a higher share of their trips than do boys; correspondingly, they are less likely to take transit (Clifton et al., 2009) or to walk. When parents chauffeur their teenagers, mothers are roughly twice as likely as fathers to do the chauffeuring (McDonald, 2006; Yoon et al., 2011). Finally, Thakuriah et al. (2009) and McCray and Mora (2011) find that young adult women are more likely to perceive difficulties in their daily travel, most notably safety.
F. Mobility and Safety
A final strand of research examines the ways in which safety—both actual and perceived—affects travel behavior and mobility. As mentioned earlier, females, both younger and older, consistently report feeling less safe than boys and men when they travel (McCray and Mora, 2011), and they travel more frequently by car as a result. However, McCray and Mora (2011) also find that teenagers tended to perceive places as less safe when they accessed them by car. Parents’ perception of safety also plays a role in mode choice—particularly in parents discouraging young females from using transit (Marzoughi, 2011). Safety concerns can also appear in other studies of teenagers and travel behavior: Trowbridge and McDonald (2008), for example, introduce their research on the relationship between sprawl and driving for teenagers by noting that teenagers have higher fatality rates per miles driven than people in other age groups.
Studies examining travel behavior and safety for teenagers can highlight important issues that studies might neglect if they focus only on accident rates. A British study by Hillman et al. (1990) finds that accident rates declined during the 1980s for child pedestrians and bicyclists, but not because Britain had become a safer place for children to walk or cycle: instead, parents severely curtailed their children’s mobility. In other words, the decline in accident rates was not an entirely positive trend.
G. Methodological Issues
The researchers who have explored the topic draw from a wide variety of mostly small data sources, such as surveys conducted near the authors’ home institutions. The National Household Travel Survey (NHTS) is one exception, however: multiple studies have relied on the 2001 NHTS (e.g., Clifton, 2003; McDonald, 2006; McDonald, 2008), and this report uses data from the 2009 NHTS. Most of the studies examine their available data at the aggregate level, which restricts their ability to examine important individual-level characteristics. For example, while some research has incorporated neighborhood data to test urban form variables, some aspects of urban form can vary greatly from household to household in the same neighborhood.
We also find no consistent definition of age categories across studies, a fact which limits meaningful cross-study comparisons. In the studies examined, the age limits for youth range anywhere from 0–19 years old; for teenagers, the ages range from 13–19. In most cases, the data available determine the age ranges rather than conscious decisions on the part of the researchers. For example, surveys administered to high school students necessarily tend to restrict the ages studied from 15–18.
Youth travel behavior remains an understudied phenomenon; nonetheless, these studies collectively present a surprisingly coherent narrative. Whereas studies of younger children’s travel have observed substantial decreases in autonomous walking and biking, and corresponding increases in parental chauffeuring over the past quarter century, the studies of travel by teenagers have by contrast observed substantial similarities between adult and (licensed) teen travel. These similarities are understandable, given that teenagers are on the cusp of adulthood. However, a few differences persist. Teens travel slightly less than adults, make fewer work and more school and recreational trips than adults, and are auto passengers more often than they are drivers. In addition, parents can continue to influence teenagers’ travel behavior directly by imposing travel restrictions or indirectly by conveying certain attitudes about a given transportation mode.
For teens, as with adults, licensing and auto access are major determinants of travel behavior. Young teens and older teens without licenses have dramatically different travel patterns than adults—specifically fewer trips and fewer miles traveled. But for licensed teens, travel patterns and choices appear to rather quickly converge on adult travel patterns with age, most notably in the reliance on private vehicles for the vast majority of travel.
Should we expect this convergence on automobility—or “auto-dependency,” as some might say—to hold in the years ahead? Or will the near-ubiquity of information and communication technologies, the recently observed drop in licensing among “middle-aged” teens (e.g., 15–17-year olds), and a persistent economic downturn collectively cause a substantial, and enduring, shift from driving? It is to these questions that we now turn.
4The earliest known work is Gurin (1974), which assesses the mobility needs of working-class suburban teenagers in Boston.
5See for example, Bungum et al. (2009), Dalton et al. (2011), Lambert and Min (2010), Landsberg et al. (2008), and Voorhees et al. (2011).
6The variation occurs because researchers use different age ranges in their studies.
7Emond and Handy (2012) report that nationally only one percent of students bicycle to school. However, the rate among high school students at Davis High School in northern California was substantially higher: 33 percent. This rate reflects the fact that Davis, California has some of the most bicycle-friendly policies in the country.