US transit has always been a place where failing to recognize civil rights becomes contested. Though most people know about Rosa Parks and the historic bus boycott in Montgomery, not as many people know about the ways in which African Americans worked through the courts to try to gain rights to equal citizenship through mobility.
David Skillen Bogen has a nice manuscript up on SSRN:
SSRN-Precursors of Rosa Parks: Maryland Transportation Cases Between the Civil War and the Beginning of World War I by David Bogen
I’m not really qualified to judge this manuscript as scholarship, as I am not an attorney, but I learned a lot reading through it about the history of segregation in Maryland following the Civil War, such as the resistance to segregated depots.