Walmart has been in the process of retrofitting parking lot lighting for years. Their first full-scale test of using LED lighting in parking lots was back in 2008 at a store in Rogers, Arkansas. Since then, they’ve been focusing on rolling out LED lighting in international markets (since those have the highest energy costs).
Here are before and after photos of an LED retrofit in a Guatemala City Walmart parking lot:
As you can see, LEDs offer visual benefits along with energy and maintenance savings. Since LEDs are highly directional, the light is better focused onto the parking lot ground, minimizing the effects of light pollution in the surrounding areas.