From page 111 of the 1918-1919 Negro Year Book, published by the Tuskegee Institute and edited by Monroe N. Work:

Railroads Attack Validity

Separate Car Laws.

The Supreme Court of Tennessee in a decision rendered in March, 1918, relative to white and Negroes being served in dining cars upheld the validity of the separate car laws of the United States, providing separate cars for white and Negroes. In December, 1918, the validity of the Kentucky law for the separation of races on trains was attacked in appeals to the Supreme Court by the South Covington and Cincinnati Street Railroads and the Covington and Erlanger Railway Company. These companies had been convicted in the lower courts for failing to provide separate coaches or compartments for Negroes.

Racism and discrimination can be expensive, and one of the only ways they can be maintained successfully is if bigots have access to political institutions that allow them to impose enormous costs on others at relatively trivial costs to themselves. Jennifer Roback has a couple of excellent articles on Jim Crow that you can access via JSTOR. Also, David Bernstein’s Only One Place of Redress is an excellent history of racist legal institutions. My paper “Inputs and Institutions as Conservative Elements” discusses racist violence specifically (ungated draft here).