In recent years online grocery delivery has become an increasingly popular service for consumers.

While the COVID-19 pandemic certainly spurred unprecedented growth in the sector, grocery delivery still remains a staple for many who enjoy the convenience, yet some wonder what the environmental impacts may be when using the service.

In response, Carnegie Mellon University’s (CMU) College of Engineering recently conducted a study examining online grocery usage and sustainability and whether there may be a better way to manage and optimize deliveries.

The study, based in Seattle, WA, looked at consumer mobility patterns between in-person shopping or leveraging a delivery vehicle. Noting that delivery personnel may travel to several homes per route tour, the study posed the question if switching to grocery delivery would reduce the number of cars on the road, improve congestion and reduce emissions.

Destenie Nock, assistant professor of civil and environmental engineering and public policy at Carnegie Mellon University.

It found that grocery delivery was actually less energy efficient than individual trips to the store, as most people stop to shop on their way home from work or at times that avoid peak-traffic hours.

“This is good because it doesn’t add to congestion on the roadways, turns out most people already try to optimize their grocery trips,” said Destenie Nock an assistant professor of civil and environmental engineering and public policy at CMU.

The study pulled government data on local traffic characteristics to run a series of experiences including:

  • Batch size: How many grocery deliveries are made in one delivery route?
  • Substitution rate: Are online deliveries being substituted for personal grocery trips?
  • Penetration rate: How many people in a given area are using online delivery?
  • Delivery time: Are orders being delivered during peak-hour travel times?
  • Grocery store location: Is the customer ordering from the closest grocery store to their home?
  • Trip type: Was the grocery trip made on the way to other destinations or directly from home and back?

Altering these factors showed little improvement in sustainability. CMU reports that even for delivery personnel with “high batch sizes of 10 groceries delivered per route” the results were still net increases in emissions and energy use.

However, the study did suggest that reduced congestion is possible when consumers buy from grocery locations close to home for peak delivery times instead of in-person grocery shopping.

CMU’s assignment model used publicly available data from the Puget Sound Regional Council (PSRC) in Seattle. The college’s work now provides a new tool that PSRC and other metropolitan planning organizations will be able to use to integrate e-commerce and grocery delivery trends into the long-range planning of the transportation system.

The trip dataset contained about 47,918 entries, each of which represented a trip that was reported by one of the surveyed individuals. The study surveyed 10,825 individuals from 5,814 households.

CMU’s full study is available for download at: