Impact of “new age” shopping behavior on VMT and the environment

By Saumya Jain

With the constant increase in retail sales from e-commerce, there have been a number of studies studying the relationship between in-store and online shopping behavior and its impact on retail-related travel. Though few studies suggest that the relationship might be complementary, a more broadly accepted idea is that online shopping, in more ways than one, is substituting for in-store shopping and can thereby reduce shopping related travel. A recent research paper shows that by not considering major demographic and economic factors affecting shopping behavior and impacts of expedited delivery options, we might be overestimating the potential of e-commerce in reducing vehicle travel and the subsequent greenhouse gas emissions.

Using data from the American Time Use Survey (ATUS), researchers from UC Davis conducted a micro-level analysis to understand how various demographic, economic, and geographic factors affect decisions to shop for goods online and in-store. For instance, they observed that increasing age was correlated with a greater likelihood of shopping in-store, and the size of the community and area of the country also influenced whether residents shopped in person or online.

The researchers used the results of the ATUS data analysis to predict how the current shopping practices of residents of two metropolitan regions, San Francisco, CA, and Dallas, TX, would change GHG emissions and VMT if they moved to online shopping. Using data from the ATUS, the 2017 National Household Travel Survey (NHTS), and previous research, the authors established an average VMT for a single in-store shopping trip and an online order delivered with other orders as 11.25 miles and 1.4 miles, respectively. The researchers then used emission rates developed by the California Air Resource Board (2018) to estimate travel-related GHG emissions. VMT and GHG emissions were estimated for two scenarios, one based on current shopping behavior—a mix of in-store and online shopping—and the other where all in-store shopping is replaced by online shopping.

Using Dallas as an example, the results show that for both scenarios, VMT and CO2 would decrease significantly due to online purchases. VMT was already reduced by around 7 percent by the online shopping that is currently happening compared purchasing all items in a physical store. If all shopping were to happen online, VMT and CO2 would be reduced by 87 percent. However, if all in-store shopping is substituted by online shopping, the results show NOx would increase by 24 percent because the current fleet of delivery trucks are heavy emitters of this pollutant.  The results in San Francisco were similar to Dallas, but altered somewhat by the different demographics of the metro population.

One other caveat is that when one considers use of expedited delivery options, the researchers observed that environmental efficiencies quickly decline, because goods are shipped via less efficient routes and with partially-empty vehicles. This point was made in a recent article about Amazon choosing not to offer specific “green deliveries” to customers for fear that it would depress purchases.

While the authors agree that there is need for further research to identify detailed stakeholder-specific roles in managing urban freight systems, they also emphasize that “the responsibility for improving last-mile sustainability is shared, beginning with the online shopper in consolidating their purchases, with the vendors and last-mile carriers in consolidating as many customers as possible into a single delivery tour, and with planners, regulators, and civic society in demanding/implementing improved tailpipe emission truck technologies.”

Saumya Jain is a Senior Associate at SSTI.