Un train peut en cacher un autre
One train may be hiding another
The original picture was overexposed outside and underexposed inside the train, with a loss of details in the seats and in the buildings and the train outside. The crossing train (the blue, red, green motion blur) was very blurry. The HDR process help recovering details in the seats and in the background. It also makes the motion blur more transparent thus revealing some details of the train in the background.