Minorities are disproportionately affected by long waiting times. Minorities have to wait twice as long to vote on average. Examples abound of people having to wait 5+ hours just to vote in heavily Democratic, minority locations. Its an easy problem to solve - add more/better locations, more voting machines, more poll workers - but seems to be consistently ignored or even exacerbated.

https://www.scientificamerican.com/article/smartphone-data-s...