BE WARNED: I have found that the Lego Freight Train can cause germestar-type vehicle explosion spam lag to servers.
Spawning a vehicle within the collision mesh of the freight train when it's sitting on its spawn can create an endless loop of vehicle explosion spam lag that can severely lag and ultimately crash servers.
This unintentionally happened to me earlier today when I spawned a freight train inside my ship's shuttlebay, and it proceeded to create an endless explosion-spam loop that nearly crashed my server from lag.