# Why moving train's windows slam shut when another train passes slowly in the same direction?

My question is related to this one but distinct as this case is trains travelling in the same direction.

We're familiar with this scenario. You're sitting in train A and another passes at high speed and your windows slam shut:

===[ train A ]=== stationary
===[ train B ]=== -> 60km/h


Often when tran B passes a bit slower the windows do not slam, e.g:

===[ train A ]=== stationary
===[ train B ]=== -> 40km/h


I'm interested in the nuanced scenario which I observer regularly, when you're travelling at medium speed in train A and train B passes relatively slowly, yet all the windows slam shut:

===[ train A ]=== -> 40km/h
===[ train B ]=== -> 45km/h


What is the explanation for this behaviour? These are the sort of windows I'm talking about - opening inwards with a reasonably strong spring that tries to keep the window either open or closed.