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.”