As the US capital traded stifling summer heat for cool autumn breezes, signs began appearing at bus stops, asking Washington commuters: what do you think about buses going cash-free?
Slowly, DC businesses are ditching paper money for plastic, embracing a trend gaining traction nationwide.
"I'm all for the cash-free system" on buses, Rogers Ferguson, a 52-year-old Washington native and Navy veteran, told AFP.
"I do a lot of travelling abroad so I'm very acclimated to not carrying cash."
The 2018 World Payments Report, released this month by consultancy Capgemini and banking giant BNP Paribas, indicates a global cash-free boom.
In 2015-2016, 483 billion transactions were cashless. That number is expected to rise at a 13 percent compound annual rate through 2021, according to the report.
Though the United States has often been a laggard in terms of payments innovations, businesses in Washington are adopting the cash-free model.
Bus operator WMATA told AFP it is exploring the concept for efficiency reasons: accepting cash can waste lots of time when customers are boarding.
But cost and security are also key factors, says James Angel, a professor at Georgetown University's McDonough School of Business.
Cash is "expensive to transport, you've got to count it, you've got to worry about it disappearing and you also have to worry about the safety of your employees," he explained.
In a country of more than 325 million people, 13 million Americans don't have a bank account, according to Federal Reserve figures.
Another 18 percent are what is known as "underbanked" - meaning they have an account, but still use alternative financial services such as check cashers and money orders.
In Washington, that translates to 37,000 unbanked and 72,000 underbanked households, officials say - meaning a whole segment of the population could be cut out of the new retail economy.
"Unfortunately a lot of the unbanked are primarily poor people, or people of color," says Stephen Taylor, commissioner of Washington's city Department of Insurance, Securities and Banking.
A lack of education, distrust of institutions and high banking fees all play a role, explains Taylor, who manages Bank on DC, a program connecting financial institutions and underserved communities.
Ferguson says a cash-free Washington could leave behind longtime residents who are senior citizens, as well as young teens and people who struggle to set budgets.
"Folks don't really know how to manage money," argued Ferguson, the father of a 13-year-old son.
"The businesses who don't accept cash really hinder their lifestyle because they can't manage it unless they physically see it."
Bumps in the road
Joseph Leitmann-Santa Cruz, an associate director at financial education non-profit Capital Area Asset Builders, said he doubts cash-free businesses deliberately exclude certain consumers.
But he notes: "Those policies are pretty much saying, 'If you are low-income and don't have a bank account or credit card, then we don't want your business".