Vehicle capacity on the northbound 405 has increased from 10,000
vehicles per hour to 11,700 vehicles per hour at peak times.
So capacity increased maybe 10k a day, or 750M over a 20 year period. Makes the $1B investment seem reasonable.
A $1B investment in public transport can buy you a whole lot more than 1.7k vph. Hell, you could reserve that new lane for buses and transport a magnitude more people than those vehicles carry starting tomorrow.
Cities are growing, suburbs are dying, you can spend the money now or face the meltdown later.
There's the meltdown on the horizon.
https://en.wikipedia.org/wiki/Sepulveda_Pass_Transit_Corrido...
Buses can already use the HOV lanes. One of the expansion lanes (the northbound one) was an HOV lane, so now there are HOV lanes in both directions. Who cares, given how few riders buses attract.