"mais au train où allaient les choses" is an idiomatic (thus very French) way to say "the way things were going". It also implies an idea of ever increasing speed. Dont be fooled by "train". It has really nothing to do with a train. (^^) Would I dare to say that "au train où vont les choses, vous risquez de finir par comprendre cette phrase"? :-)

yes, "au train où vont les choses" means " à la vitesse où vont les choses". But I wouldn't say that it's idomatic, since you can find other examples. Train is an rather old way to say speed, it's exactly the same meaning. Here are some quite common expressions: "rouler à un train d'enfer" = "rouler très vite" "à un train de sénateur" = "à une vitesse de sénateur" = lentement and also "le train-train quotidien", here the repetition of "train" gives a "boring" feeling

Ca signifie "a la maniere (et la vitesse) dont les choses se passent"