All across the world, small projects demonstrating driverless buses and shuttles are cropping up: Las Vegas, Minnesota, Austin, Bavaria, Henan Province in China, Victoria in Australia. City governments are studying their implementation, too, from Toronto to Orlando to Ohio.

And last week, the Federal Transit Administration of the Department of Transportation issued a “request for comments” on the topic of “Removing Barriers to Transit-Bus Automation.”

The document is fully in line with the approach that federal and state regulators have taken, which has promoted the adoption of autonomous vehicle technology as quickly as possible. Because most crashes are caused by human mistakes—and those crashes kill more than 30,000 Americans per year—self-driving-car proponents believe that the machines will eventually create much, much safer roads. For example, some researchers contend that fatalities could drop 90 percent, which would be a public-health triumph.

As people consider the negative repercussions of such a change, the obvious problem is that many people drive for a living. Much of the discussion has focused on truck and taxi drivers. In part, that’s because of the scale: there are more than 3 million truckers of various kinds in America. In part, it’s because Lyft and Uber have concentrated attention on the ride-hailing labor market. Transit operators, however, have rarely entered the debate, even though there are more than twice as many bus drivers (687,200) as taxi drivers (305,100), at least as measured by the Bureau of Labor Statistics.

The truck-driver discussion also slots nicely into the white working-class narrative around automation. Unionized, male factory workers were displaced by new machines; white, male truck drivers might be pushed out by self-driving big rigs. And it is true that automation threatens to displace many kinds of workers, as report after report has shown.

But, in the specific case of driverless buses and the general case of employment, the African American experience of automation is specific, distinct, and important to consider. Not all job displacement is created equal.

First, the history. Scholars like historian Donna Murch, author of Living for the City: Migration, Education, and the Rise of the Black Panther Party in Oakland, California, have integrated the introduction of mechanical cotton pickers into the story of the Great Migration in which 6 million black people left the rural south for urban areas in the the west and north. Murch argues that while a complex set of factors, including the push of Southern racism and the pull of wartime jobs, touched off the migration, agricultural automation accelerated it. As black workers began to leave, big farmers turned to machines to fill their labor shortage.

“In order to secure production, planters ultimately turned to mechanical cotton pickers, which quickly made large numbers of sharecroppers and farmworkers extraneous,” Murch writes. “In the final stages of mechanization, obsolescence replaced the acute labor shortage almost immediately. By the mid-’50s, rural-to-urban migration had become a necessity rather than a choice.”

Arriving in the cities of the north and west, black Americans faced housing discrimination and exclusion from employment. Just as they were securing a foothold in the new cities, those cities began to crumble as their manufacturing industries abandoned them. A second wave of automation decreased the need for black labor, and what manufacturing outfits survived began to relocate out of the urban core. So, at the exact moment that the civil-rights movement was opening up industrial unions and jobs, many factories were closing in the places where black people were forced to live. In the San Francisco Bay Area, for example, that meant factories closing in Oakland only to reopen in the (nearly) all-white suburbs to the south.

Given all these conditions, black people turned to civil-service jobs as a stable and un-relocatable source of employment for black people. Government jobs were less discriminatory, too, with a smaller wage gap between black and white workers than the private sector. In 2011, the scholar Steven Pitts at the UC Berkeley Labor Center found that black workers were 30 percent more likely than other people to be government workers. Add it all up, and Pitts declared: “The public sector is the single most important source of employment for African Americans.”

At least, that is, once activists were able to overcome the discriminatory hiring practices within these organizations, a story that Katrinell Davis, a sociologist at Florida State, traces in her book Hard Work Is Not Enough through the Bay’s AC Transit. After black workers broke into these jobs, however, they provided crucial stability.

“For decades, public-service employment has been the primary means to wage security and upward mobility in the black community in the Bay Area as well as in every metropolitan area in this country,” said Davis. “Local and state government jobs were once great opportunities for workers, especially women of color. Jobs in this sector in many cases were unionized and subject to nondiscrimination legislation since the 1940s that benefited workers who were hard-pressed to find similar work with private employers.”

This is the historical backdrop for the driverless bus. When factoring the negative externalities of autonomous buses, this is the history that must be considered. More generally, Davis said that black workers were likely to be disproportionately hit by widespread further automation.

“Automation poses a disproportionate threat to the economic well-being of black America because this social group is predominately employed in low-skilled occupations that are vulnerable to workplace technological innovations—like those employed in the manufacturing, trucking, retail, and the telecommunications industries,” Davis said. “Now, workers employed by public transit authorities, their unions, and their patrons must contend with the introduction of driverless coaches.”

At least one union, in Ohio, has tried to get ahead of the issue. Local 208 of the Transportation Workers Union saw that the Central Ohio Transit Authority was envisioning deploying driverless buses by 2025, and began a campaign to draw attention to that possibility.

“It would be devastating in the African American community as predominantly the bus drivers are African American,” the president of the local, Andrew Jordan told the local NPR affiliate. “And to displace the well-paid middle-class jobs in those communities would be devastating.”

For Davis, the sociologist, the unions no longer hold the power they once did. Over the last couple of decades, as more black people have obtained government jobs, civil-service workers have been painted as “lazy, unreliable, and undeserving of wage increases.” For Davis, it’s this “history of mistreatment” that “paved the way for machines to take over.”

“I think that driverless technology is an extension of the economic oppression that has been in place since the African slaves were emancipated and free to sell their labor,” she concluded.

As self-driving technology moves closer and closer to actual deployment, it will cease to be solely a fascinating technological story about machines’ capabilities. Once it escapes the lab, the real reckoning of how and where autonomous technology should be deployed will begin.