Wyoming 789 is noted for being expanded southwest of Riverton (Oct 2014 article):
http://county10.com/2014/10/22/bid-awarded-expand-south-wyoming-789-riverton-five-lanes-accommodate-casino-traffic/
Quote$11 million to widen a 3.3-mile section of WYO 789 south of Riverton from two lanes to five lanes. The section includes a bridge over the Little Wind River. The highway section has been carrying growing traffic volumes since the opening of the Wind River Hotel and Casino. The project is scheduled for completion by June 30, 2016.
I traveled through this area in 2010 and noted quite a bit of traffic on Wyo 789 between Riverton and Lander.
Definitely needed. Lots of traffic to/from the casino and Lander.
Didn't know 789 was still a major highway in Wyoming. Then again, it goes from Montana to Colorado, so...
Not to mention, parts of it are by Yellowstone, which will DEFINITELY jam up traffic. Like on US 14 ALT between Cody and Lovell, WY, that's four lanes just because of the park along with the Grand Tetons.