It will not reduce traffic in cities. the terrible traffic in san francisco and los angeles is not caused by traffic between the two cities. Rather, it is caused by traffic in each of these cities metro area.

Right now, If I want to go to Los angeles from my home city of San Francisco, I have two options; fly on southwest or drive. Lets compare the two:

Fly on Southwest: It is very easy and quick. If i am going for a day trip, I would drive to OAK or SFO. Excluding driving to the airport, here is a breakdown of the time:

– Parking (assume i am going for a day trip, so i park at the closest parking): 15 minutes
– Security 15 minutes
– wait at gate – 30 minutes
– transport time – 90 minutes
– walk from gate to taxi at BUR or SNA: 15 minutes
– total time: 2 hours 45 minutes

Lets look at alternative to take a train to los angeles metro area:
– Parking (assume i am going for a day trip, so I will park at the closest parking): 15 minutes
– security – 15 minutes
– wait at train station – 30 minutes
– transport time acording to state of california website: 2 hours 45 minutes
– catch a taxi: 10 minutes
total time: between 3 1/2 and 4 hours.

Why would I take the train? Flying is the better option.