Source: US DOT, 2017 National Household Travel Survey.
Each trip is undertaken to satisfy the purpose and the nature of this purpose is illustrative of a very specific mobility context in terms of the time of the day and even to mode used. The above graph provides a breakdown of the main categories of household trips by purpose in the United States. Since most of the population is urban, this distribution reflects the purpose of urban trips. While from the 1980s to the 1990s, the number of trips per household was increasing, reflecting growth in mobility, the number of trips has since then receded. This is particularly the case for shopping and personal trips, which are influenced by. changes brought by the availability of online information and e-commerce.
Although different urban settings will have different trip compositions, most of the trips undertaken in urban areas across the world are work-based:
- Work. Commutes performed towards the workplace, which represent approximately 17% of daily commutes.
- Business (work). Trips from the workplace to a business destination.
- Personal. Trips related to personal activities such as restaurants, the library, or the post office.
- Shopping. Commutes towards any store regardless of its size, merchandise, or whether or not any purchases are made. These commutes represent approximately 18% of all daily travel.
- Social and recreational. Social trips are related to activities such as visiting family and friends. Recreational trips are performed with the intention of recreation such as cultural or sports events. These trips represent about 27% of daily commutes.
- Education. Commutes towards a learning establishment by those seeking any type of training, regardless of the level of learning. These commutes represent 10% of the daily travel total.
The accumulated total of commutes terminates at home since every commute involves a round trip back home. This is referred to as the symmetry assumption; any trip from home is usually accompanied by a corresponding return trip at the end of the day or given activity.