I agree with your calculations, but with an 1g acceleration for 25s, the train will travel a bit more than 3km, and getting to the end of the track (which is 3k

I agree with your calculations, but with an 1g acceleration for 25s, the train will travel a bit more than 3km, and getting to the end of the track (which is 3km according to the article) at close to 900km/h is unlikely to lead to a happy outcome. If my math is right, in order to accelerate to 900km/h and decelerate to a stop again, all on a 3km track, requires acceleration/deceleration of a bit more than 2g.