New Ideas for How Cities Can Stop People From Littering

Cities across the United States are struggling to deal with litter. In addition to its negative environmental and health impacts, litter abatement costs local and state governments $1.3 billion each year. The pandemic has made matters worse, with garbage collection staff shortages and new types of improperly disposed of waste, like personal protective equipment.

Because littering is an inherently behavioral problem, local governments typically invest in signage to encourage people to throw their trash away properly. Yet 90% of U.S. residents already think that littering is an issue.

So do signs shift behavior?

New research suggests they do not—at least not enough to be worth it. With this evidence in hand, we can point to more effective long-term solutions for cities.

Testing the Impact of Signage in Indianapolis

In 2021, the nonprofit, Keep Indianapolis Beautiful (KIB), and the Indianapolis Office of Sustainability found that signs had little to no impact on the amount of litter at bus stops. The Behavioral Insights Team set up the study to test anti-littering signage informed by behavioral science, which is the study of human behavior and how our actions are shaped by environmental and contextual factors.

The 206 bus stops in the study already had trash bins or bags. We added signs encouraging riders to use the waste infrastructure. We also randomized which bus stops the signs were placed to limit the influence of outside factors on the results. Half received new signage, and the other half remained unchanged. We measured pieces of litter, cigarette butts and whether the bus stops were serviced by cleaning crews over the course of three weeks.

Bus stops with new signage had one less piece of trash on average compared to the unchanged stops (about 14 pieces of trash versus 15). That’s not enough to rule out that the difference was due to chance.

A Multi-city Study on Cigarette Butt Litter

Results from Indianapolis build on a growing body of evidence showing that signage does not help reduce litter. Dr. Wesley Schultz, a psychology professor at California State University San Marcos, conducted a study in Columbus, Ohio, Memphis, Tennessee and Shreveport, Louisiana focused on cigarette butts, the most littered item on Earth. His team tested whether cigarette butt collection stands, public anti-littering advertisements or a combination of the two would reduce cigarette butt litter.

Community crews cleaned the 72 sites before the new stands and advertisements were installed to ensure a consistent baseline. The results showed that cleaning up existing litter alone reduced cigarette butt litter by 48% after three months. Adding collection infrastructure reduced litter by an additional 20%. Advertisements did not enhance the effects of either. In Indianapolis, signage also appeared to have no effect on cigarette littering behavior.

Why Littering is Tough to Stop

Behavioral science tells us that people tend to choose the easiest way to achieve their goals. Generally, we also value instant benefits over long-term gains. When it comes to trash, our goal is to get rid of it quickly, especially when we are out of the house. But unlike a behavior such as drinking, where we experience its negative consequences (a hangover), there are few immediate personal repercussions to throwing garbage on the ground.

Anti-littering signage is a tempting solution for cities because it is relatively low-cost and has been shown to work well indoors and on sidewalks. But thanks to decades of national anti-littering campaigns, many people already know that littering is wrong. Even fines do not appear to be a strong deterrent. Unless other changes are made, the convenience of littering will win out.

Littering solutions

To effectively reduce littering, cities should invest in strategies that:

• Prevent waste from being created in the first place.
• Make it easy and attractive for people to dispose of trash properly.

Preventing waste from being created can look like disincentivizing single-use plastics through fees on plastic bags or changing how people think about them. Facilitating goods repair and exchange networks and finding accessible ways for residents to reduce food loss may also help, but might be tougher for local governments to implement.

Cities can make it easy for people to dispose of trash properly by changing residents' physical environment. For example, improving the look and location of trash cans and strategically adding more to sites where people are likely to need them: city centers, outside dining and retail establishments and recreational areas.

Informing residents about free trash pick-up services could also help. In another study we conducted with KIB and the city of Indianapolis, we found that informative mailers had an immediate impact on proper disposal of heavy trash. Households that received a mailer were about 55% more likely to set out waste for collection.

Shifting the social norms of a space may also make proper disposal more attractive. If areas are already clean, people are more likely to keep them that way. In his multi-city study, Dr. Schultz found that cleaning up existing debris cut new cigarette butt litter by nearly half. Cities can organize similar community cleanups to change social norms around littering.

As more research is done on strategies to prevent littering behavior, we hope that local governments think twice before investing in signage. We have strong reason to believe that cities and states would be more successful directing funds toward infrastructure that will stop waste from being created and make it as convenient as possible to dispose of trash correctly. If you are interested in exploring behavioral solutions for littering in your city, contact the Behavioral Insights Team, who is part of the What Works Cities Certification program.