The 2001 NHTS captures various aspects and characteristics of daily and long-distance travel in America. Data collected on daily trips include topics such as the purpose of the trip, the means or mode of transportation used, the duration and length of the trip, the time of day and day of the week when the trip took place, and the number of people in the vehicle during the trip. In the 2001 NHTS, a daily trip is one that occurred on the randomly selected travel day regardless of mode or distance traveled, as long as the person went from one address to another. This section focuses on daily passenger travel.
Results from the 2001 NHTS show that daily travel in the United States totaled about 4 trillion miles (table 2, table A-8), an average of 14,500 miles per person per year. On a daily basis, the average person traveled 40 miles, most of it (35 miles) in a personal vehicle. Because more than one person can travel in a personal vehicle, these 35 person miles amounted to about 23 vehicle miles traveled. Annually, the total number of vehicle miles traveled in 2001 was nearly 2.3 trillion.4 In terms of number of trips, people took 411 billion daily trips in 2001, or about 1,500 trips per person in that year (table 2).
On a daily basis, individuals averaged about four trips (figure 5, table A-9). Although there were no differences in the total number of trips taken based on gender, there were differences based on age. The total number of trips peaked among the working population aged 25 to 54 (4.6 trips on an average day). Children under the age of 5 had the fewest trips on average (3.2 trips), followed by children between the ages of 5 and 14 and adults over the age of 65 (figure 5, table A-9). Not surprisingly, drivers and employed adults had a higher number of trips (4.5 trips for both groups) compared to nondrivers and unemployed adults (2.6 and 3.7 trips respectively) (table A-9). The NHTS also collected information on the travel behavior of persons 15 or older who have a medical condition that limits their travel. About 8.6 percent of persons report having a medical condition that limits their travel (table A-1).5 As would be expected, these persons had lower trip rates (2.8 per day) than those who did not report any such medical condition (4.4 per day) (table A-9).
The majority of daily trips occurred in personal vehicles (87 percent) (figure 6, table A-10). About 38 percent of all trips were personal vehicle trips with a single occupant (driver only) while 49 percent of all trips were personal vehicle trips with more than one occupant. About two percent of all trips nationwide were transit trips.6 School buses accounted for almost 2 percent of the trips, and walk trips accounted for almost 9 percent of all trips.
Knowing why people take trips helps urban planners lay out residential, work, and commercial structures that minimize travel times and distances. A large portion of trips were taken for family and personal reasons such as shopping and running errands (45 percent) (figure 7, table A-11) (See glossary for definitions). Social and recreation trips, such as vacations and visiting friends, accounted for 27 percent of the trips. Despite the strong focus on work and commuting trips by researchers and urban planners, commute trips7 accounted for about 15 percent of all trips taken in the United States. Trips made for work, other than the commute to and from work, accounted for an additional 3 percent of trips. Trips to school and church accounted for about 10 percent of all trips.
Congestion is a concern for urban planners and drivers alike. Fifty percent of adults in the United States say that they are somewhat to severely concerned about highway congestion (table A-1). Daily trips (including nonpersonal vehicle trips) are not spread evenly across the time of day, however. Nor are strong peaks and valleys associated with the morning and evening commute periods (figure 8, table A-12). For example, more daily trips are taken between noon and 1 p.m. (7.4 percent) than between 8 and 9 a.m. (5.5 percent). Daily trips are spread more evenly across the days of the week. The fewest trips are taken on Sunday (13 percent) compared to Friday, when the most trips are taken (16 percent) (see table A-13).
Vehicle occupancy can be conceptualized as a function of both the number of people in the vehicle and the distance traveled on the trip. Thus a trip of 12 miles has twice the weight of a 6-mile trip. In general, the weighted (by miles traveled in trip) occupancy rates of personal vehicle trips in the nation is 1.6 persons per vehicle mile (figure 9, table A-14). There are differences in weighted occupancy based on the purpose of the trip. Trips for social or recreational purposes have an average weighted occupancy of 2.1 persons per vehicle mile compared to work trips (1.1 persons per vehicle mile) (figure 9, table A-14). Other factors affecting weighted occupancy rates are time and day of travel. Weekday trips have a weighted occupancy of 1.5 compared to 2 people per vehicle mile on weekend trips (table A-15).
Given that a majority of daily trips are in personal vehicles, it is of interest to know how much of an adult's8 day is spent behind the wheel driving a personal vehicle. Overall, for all adults, including nondrivers and those who may not have driven in a given day, 55 minutes are spent behind the wheel driving 29 miles a day (figure 10). There are differences based on adult demographic characteristics such as age, sex, and worker status. Even though men and women average the same number of trips (4 trips) on each day, men drive further (38 v. 21 miles) and longer (67 v. 44 minutes) (table A-16 and A-17). Similarly, there are differences based on the age of the adultthese differences mimic the pattern of the overall total number of trips taken (figure 10). Teenagers drive the least on an average dayfor about 25 minutes and 12 miles. Adults over the age of 65 also drive less on an average day compared to other adult age groups (20 to 64 years)39 minutes and 17 miles. Adults between the ages of 25 and 54 drive the most64 minutes and 35 miles a day. Workers drive further (36 v. 16 miles) and for longer (65 v. 35 minutes) compared to nonworkers (tables A-16 and A-17).
4. This compares to 2.1 trillion vehicle miles (standard error 23.4 billion miles) traveled in 1995, an increase of about 11 percent between 1995 and 2001. (1995 Nationwide Personal Transportation Survey).
5. Individuals 15 and older were asked if they had a medical condition that made it difficult to travel outside the home. This is a self reported condition, and does not correspond to the Americans with Disabilities Act of 1990 or other formalized definition of a person with a disability.
7. Commute trips are defined as those trips made for the purpose of going to or returning from work. However, given the definition of a daily trip, those reported as commuting trips were not necessarily anchored by the respondent's home or workplace (for return commutes). Therefore, care should be taken in analyzing work trip distances, recognizing that the distance for these trips is often, but not always, the distance from home to work.