Resurrecting this because some work is FINALLY being done along Lamar Ave/US-78. Just in time for me to move after having driven up and down that road for the past 10 years!
TNDOT started doing earthwork roughly 60 days ago, appears that they're going to start widening right at the MS/TN state line, and proceeding up to Shelby Dr at this point. Major earthwork has been ongoing around the Holmes Rd intersection, which looking at the bid documents, will be grade separated (they're only 20 years behind on that!). There also has been some work being done to the bridge just north of Shelby Dr crossing John's Creek, but work is only being done on the WB side, so it may just be an emergency repair. Not surprising given the decrepit state this road is in along its length.
Speaking about the road in general, most of the congestion, at least in my opinion, is self-inflicted on the stretch between the state line and Winchester Rd. There has been little to no effort put into mitigating the impact of the traffic lights along the road. Several intersections have left turn signals that turn on when the left turn lanes are unoccupied, or needlessly give greens to non-existent traffic (Tuggle Rd, I'm looking at you!) on one side when a car is waiting on the other side of the intersection. Get a green at one light, just to have the next one flip to red a quarter mile away. Factor in trucks two abreast on the road most of the day, it is difficult for traffic to maintain any kind of even flow with it being so regularly broken up by the lights on the road.
Looks like the completion date is slated for 2021, so I'll (thankfully) be long gone before it is done.