There are 300+ people on a train and 4000+ on a cruise ship, those things don't need to be used as a weapon to cause a very sad day for the whole Nation in terms of human lives lost.
Even if the thing is not used as a weapon.
For trains, the situation is similar. Even if you manage to bomb a train, it's unlikely to cause a major, deadly disaster. Rail infrastructure is built with the assumption that trains will get out of control, and the industry has nearly 200 years of experience.
Trains, ships and airplanes are ineffective weapons that need a lot of knowledge to turn into an actual weapon. A truck is way more effective: easy to acquire, easy to use, and even right in the middle of an attack people will assume that the driver has lost control or has medical issues instead of being a terrorist.
In trains with a separate locomotive, passengers cannot even get to the driver compartment. In any electrified rail scenario, a runaway/commandeered train can be stopped by removing the power supply and then diverting the train onto catch points. Not to mention that running a red light triggers an automated immediate brake in many rail systems.
Of course, breaking into a parked locomotive, starting it and overriding the safety systems (deadman switch, red light detector) is possible, but it requires a lot of training you won't find online, and without the cooperation of someone at the control center all you're going to do is to derail the engine (as usually, there is a catch point switch at the entry of every branch onto the main track, that is by default pointing to the catch point).
> Also the 10000+ souls at the departing and arrival train station also don't matter.
Agreed, but bomb/poison threat is a risk at every large building.
> Not to mention the 4000 souls aboard cruise ships.
It's incredibly difficult to pull off a fatal attack using a commandeered (cruise) ship as a weapon - wannabe pirates would need to control the entire bridge and the machine room as well as any auxiliary control points (e.g. for guides) that allow a remote shutdown of the engines. And even assuming attackers do gain control of a ship... a ship is slow, and cost guard will intervene if they notice you on a dangerous collision course.