Just drove through that stretch and saw that somebody lost many, many cases of nails. They're banded nails for nail guns, but the sets are being broken up as people drive over them. I'd guess that they're spread out over about a 500m stretch. You might want to give that road a miss until they clean it up...and even then, can you really get them all?
Location: Westbound, Marine Way, east of Byrne Road.