Layers of tunnels to add traffic lanes

After the https://en.wikipedia.org/wiki/Interstate_Highway_System little has been done to significantly improve traffic flow. The populations have ballooned while road lanes have not.

Many places were designed street widths for a certain amount of traffic. The streets are now adjacent building locked so they can no longer widen them to accommodate the massive amount of traffic during the rush hour.

Since lateral road expansion isn't possible without razing buildings, we are left with vertical expansion. Going up with say double decker roads would be unsightly, no one would go for that. This leaves underground tunnels as the only real solution for adding more lanes. Only so many opt for mass transit such as buses and trolleys, many want the freedom and flexibility that automobiles afford

So much talk about housing crisis with little mention of the associated traffic crisis. People also need more lanes not just more houses. Less time on roads means more time to be productive. I suppose self driving cars will make waiting in traffic more bearable in the mean time as you'll then be able to do many of the things you'd do when you got home, such as check email.