People of color are often over-represented among transit users, with significantly less variability in over-representation than seen in data on walking to work. This chart shows that relationship for 76 cities in all 50 states.
People of color are more likely to live in larger cities were transit options tend to be more comprehensive, and are also less likely to have access to an automobile. The often limited connectivity and reliability of public transit in the US due to the focus of most transportation policy towards automobiles means that a disproportionate reliance on public transit can be an indicator of limited access to opportunity.