The history of the US Route System in Las Vegas

[The Ghostbuster]

I think they should leave Boulder Highway as a six-lane boulevard. Narrowing it to four lanes would likely increase congestion, especially if they were to add a light-rail line to the median. I'd be okay with a bus lane being added as long as it utilizes the existing curb lane.

[fungus]

I think you could narrow the lanes and do the low speed frontage road concept for the right lane. I haven't driven down Boulder Highway in years, but it sure looks like much of it has the original 1960's era configuration of the dirt median, like Las Vegas Boulevard used to have.
https://www.google.com/maps/@36.1540434,-115.1109558,3a,75y,323.09h,77.95t/data=!3m7!1e1!3m5!1sk-84W_-zbDwp739zvKENPQ!2e0!5s20211201T000000!7i16384!8i8192?entry=ttu