Which date, what time flights?
To ask about this is to verify that you need to avoid Morning rush or not.
The delay of itn'l flights is the biggest cause due to weather conditions,
but if it is regular flights you can confirm 7 days flight history at "Flightradar24
" in advance.https://www.flightradar24.com/
(sample, no need "log in", free)https://www.flightradar24.com/data/flights/jl11
Transportation btw airports is detailed in both airport sites.
There is also a direct bus that goes through the bay area,
also direct trains(no seat reservation) are operating after morning rush hour.
The bus runs also during morning rush hour,
but there is a bit risk by traffic jam(not so serious) or accident.
Also by rail possible during rush hour,
but it is caught in congestion due to the transit in the downtown area in Tokyo.
You can search at Google MAP and HyperDia very easy.
The fastest train is around 85 min
via Nippori by LtdExp SkyLiner fr NRT and Shinagawa.
(Keisei - JR-East - Keikyu/railway companies)http://www.keisei.co.jp/keisei/tetudou/skyliner/us/index.phphttp://www.keisei.co.jp/keisei/tetudou/skyliner/us/ae_outline/index.ph...
This is direct train (Not LtdExp) is about 90 min.http://www.keisei.co.jp/keisei/tetudou/skyliner/us/nrt_access/index.ph...
Direct bus is about 80 min if no traffic jam and accident.
You can check real time traffic conditions at Google MAP,
but can not predict the future a few minutes ahead.https://goo.gl/maps/Lx8NweE2muN2
Bay area Expway(Wangan line) is wider than mid Tokyo, but larger trucks a lot.http://neko-expwy.up.n.seesaa.net/neko-expwy/image/KASAIJCT01.JPG
So train is safer if it is a holiday(SAT, Sun, National holidays) or Rainy day.