LA is building a rail parallel to the 405, and the Silver Express (bus) has run down the 110 for more than a decade. LA is also building 2 more rail lines in the SFV. The reason they're not already built is that the SFV opposed these lines 3 decades ago when they were originally proposed and only recently dropped its opposition.
Also, Buses run from downtown to Beverly Hills, and getting from Long Beach to Brentwood can be done entirely by public transportation.
Sorry, I see now the above comments are more a refutation than a statement of, "Look how good the transportation system is." I'll leave these though just to make my general point about how horrible the options are.
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Just pulled up google maps for Long Beach to Brentwood:
To be fair, that was at 7:30pm, the tail end of traffic and after the busses switch to a reduced schedule. I'd be curious to see those results at 5:30pm.
Plenty of people still need to get around at 8PM at night. So, I'd say a bodega worker in Brentwood going home to their less expensive apartment in Long Beach would prefer to be able to commute home at 10PM without it taking 3 hours :)
Also, Buses run from downtown to Beverly Hills, and getting from Long Beach to Brentwood can be done entirely by public transportation.