While my heart is for non-automobile transportation, any alternative to road widening is a good alternative. And that means making more efficient use of existing roadways. The least efficient part of the urban road network are the intersections. 100% of the traffic volume from two streets trying to share the same space by taking turns. And every time the other road gets it turn, and the lights switch, everyone has to start up and get up to speed. Just in time to slow down and stop at the next light, and then stand idling. Extremely inefficient. The obvious solution is to double the space of the roadway. But that's very problematic because of big rigs. Every bridge needs to be tall enough to drive a semi-truck under, strong enough to support (multiple) semi-trucks at once, and gentle enough curves and slope that you can drive a semi-truck on it. As you can imagine, that tends to make overpasses very bulky bits of construction.
Which is why I'm always pleased to see new alternatives to full interchanges. Bangerter Highway is proving a very innovative area. It already has two Continuous Flow Intersections (CFI) and there are plans to try out some other new tricks, such as the 'Center-Change'. According the Deseret News, the idea is in planning for the 3100 and 4100 South intersections at Bangerter Highway. While the construction will suck, it seems like a worthwhile change. The CFI intersections were certainly a major improvement over the previous 'Dual-Left-Turn' intersections.