Walmart mandates one-way aisles.

And masks for employees. N95 masks will not be used, they will be saved for healthcare workers.

This could be interesting since Walmart has a very hard time even keeping its shelves neat.

https://www.ajc.com/news/walmart-mandates-one-way-aisles-employees-masks-gloves-response-coronavirus/pUlG9XFkf5AWkIyhA2FV7O/

EDIT May 22, 2020: Meijer, centered around Michigan and the midwest, also wants people to move one way down aisles but no one is enforcing it. Meijer has put arrows down each aisle on the floor. No one is enforcing mask use at Meijer either.