OT: Who's responsible for cleaning Michigan highways, interstates & exit ramps?

I travel all over the state for work and it bothers me to see how filthy most of our highway system is. When all that Amazon hoopla was going on I couldn't help but think if they scouted the area it would unfortunately take them all of 10 minutes of driving around Metro Detroit to be disgusted. That said, some small sections of I-75, I-94, I-96, US-23 appear to be very well maintained – a few exit ramps are spotless and have extraordinary landscaping (e.g., Auburn Hills). The state's marketing is lakes, nature, outdoors, fresh air ... copious amounts of litter, debris, fast food waste, soda bottles, hubcaps and blown out shredded tires is so incongruent of the brand. I don't get why this isn't a top priority. I've reached out to MDOT (they have a $4 billion annual budget) and they blame others, I've reached out to local gov and they blame MDOT – either way, it's obvious neither really cares.