On an annual basis, people in the United States make about the same number of trips on weekdays (56.3 billion) as they do on weekend days (62.7 billion)1 . However, trips made during the week are heavily concentrated in the morning and evening rush hour peaks (figure 4-6). Weekend trips, by contrast, are shifted more toward the middle of the day and peak later in the evening. One of the busiest hours of any day for trip starts is 6 p.m. to 7 p.m. on weekend days. The most common purposes for these trips are people going home from an activity and people going out (say, to eat) or to buy goods and services (e.g., groceries or video rental).
The large number of weekday trips beginning between 7 a.m. and 9 a.m. are predominantly people traveling to work and school (figure 4-7). A large number of trips during the afternoon peak are people returning home from work and school, but this is mixed in with people running errands (e.g., shopping) and making trips for social and recreational purposes. These patterns are linked with the modal pattern that shows that weekday transit trips are more concentrated than trips by personal vehicle, particularly in the morning rush period when work and school trips overlap and travelers are less likely to be making other types of trips .
Social and demographic characteristics are another influence on the distribution of trips throughout the day. For instance, weekday time of departure by age reflects the different opportunities and constraints of travelers. Those 20 and under have the most concentrated profile of trip times reflecting the beginning and ending of school and their heavy reliance on others for transportation. Those aged 66 and over are typically less constrained by work hours and thus make a large number of trips between the morning and evening rush periods (figure 4-8).
The concentration of trip-making at certain times of the day can often place a strain on transportation infrastructure. The morning and evening "rush hour" is the most obvious example. But when a trip is made varies with a range of factors including, among others, day of the week (weekend vs. weekday), transportation mode, purpose, and social and demographic characteristics.
1. U.S. Department of Transportation (USDOT), Research and Innovative Technology Administration, Bureau of Transportation Statistics and USDOT, Federal Highway Administration, 2001 National Household Travel Survey, CD-ROM, February 2005.
1 Standard error data are available in tables 4-6 through 4-8 in appendix B.