How can you let someone know they are about to loose something on a 2 lane road? We seen this grill that looked like it was strapped on with ratchet straps slowly shifting position and couldn't think of a way to alert the driver as I didn't want to get to close. The road had lots of traffic going the other way with quite a few motorcycles. The driver was going like a BOOH when, Poof, it went, in a cloud of ash dust but it hung on while losing parts. I kept my distance in case it came loose and they dragged it about a 1 ยฝ miles when a guy in a pickup on a side road noticed it and chased them down and passed them on the right. I took the photo just as he was pulling over.
To answer the OP's question, don't create more risk trying to get alongside the driver on roads like that. Flashing your brights and honking your horn are the best options in a situation like that. And keep a safe distance.
We were behind a Denali towing a 30' TT with 3 bikes strapped to the rear not long ago. They were bouncing up and down severely, and the brackets must have been taking a horrible beating. Just another reason to constantly maintain awareness when traveling.
It sounds like a good one but, it can't top the RVer who Drug His Truck for Several Miles while it was in gear/park and burnt a tire off. After being advised of the situation, the RVer drove away, still dragging the tire.