Construction to add a toll lane each direction will begin next month, it will be interesting to see how they acquire the ROW for this project considering there are train tracks in the median and neighborhoods right up to the shoulders:
http://www.kxan.com/news/local/austin/mopac-toll-project-to-break-ground-in-october
According to the reports I've seen, new right-of-way won't be needed. Well, it's needed, but it isn't feasible to buy any. They'll add narrow strips of pavement to the inside and outside of the roadways, within existing right-of-way, and in some parts the lanes will be narrowed from 12 feet to 11 feet to make everything fit.
Is this really an expansion? Congrats NIMBYS in Terrytown, you win again.
Oh boy, I can't wait of it to begin. Mopac has gotten worse as an "alternate " to I-35 in the past 15 years to the point that now it is a total joke. So with construction it will be a mess for years.