I'm not sure that's true, just providing alternative transportation doesn't by itself control congestion-- London has good alternative transportation options, b

I'm not sure that's true, just providing alternative transportation doesn't by itself control congestion-- London has good alternative transportation options, but also has a £15 congestion charge (i.e. toll) to limit traffic during peak hours. If the roads are free to use and not congested, many people will use them until the cost or inconvenience of using the road is greater than the alternative transportation. (that's not true of everyone, of course, some will use alternative transportation even at greater cost or inconvenience)