Good morning:)  I suspect aversion to gridlock is a factor, both here and elsewhere, for increasing numbers of younger generations foregoing car ownership (e.g another post in this thread said 39% of Oahu residents don't have drivers licenses, but I do not know how that breaks down by age if true).  

But I am not as "certain" as you seem to be that gridlock is the primary reason--either locally or nationally.  My impression is other factors are bigger, such as younger people increasingly can’t afford to “have it all” due to more student loan debt, inadequate incomes, and out-of-reach housing costs. 

TOD is ostensibly intended to create more "affordable" housing while also reducing transportation costs.  But I never thought rail would significantly reduce traffic, and am not convinced rail will reduce housing and trans costs.  I think much cheaper options already exist, e.g. tele-work and ride-sharing, which could be generously incentivized and still cost far less than rail.  Aloha:)