Last time I was in northern Indiana they were putting finishing touches on an upgrade of US31. Now it is interstate standard divided highway from Indianapolis to Lake Michigan (or nearly so). My inlaws old house used to have drive way off of 31 as it left South Bend. Then it was widened to 4 lane, and their drive way was rerouted around the block. And with the latest change the house was bought up by the state.
So access to that area changed from drive way to cross street to interchange. Cars now zip by without seeing the lovely old houses, or downtown South Bend. The corn fields are off in the distance, not right next to the highway. The tollway used to be the only divided highway in the area. Now US20/31 bypass lets people zip between South Bend and Elkhart and beyond across the south side. RVs can return to their birthplace in Wakarusa (or elsewhere of IN 19) without going through either downtown. Historic Lincoln Hwy east of Elkhart is being divided (or twined to use a Canadian term).
They doing that because traffic levels are too high for safe and fast travel on conventional 2 lanes highways. And simply adding lanes in a suburban environment doesn't help when you also have drive ways, cross streets and stop lights.
2 lanes are fine across rural eastern Colorado. A bit less so across the mountains of Colorado and Washington, where trucks and slow RVs hinder traffic as they crawl up or down the grades.
People ask about alternatives to I80 across the south side of Chicago. The next highway to the south is US30, stop and go across the southern suburbs. The next option is some state numbered highway (27?) much further south. Or I70 through Indianapolis.
The pros and cons depend strongly on the alternatives in a particular area.
