But maybe it's MC's current technical abilities that would be the limiting factor?
His production ability cannot freely create effects, yes. While there is magic and some wondrous effects can be made, it still follows certain principles (hence why the fire broke out...because enchanting something with fire still is a potential fire hazard).
He has no time for necessary research.
On another note, the distance is roughly 590 KM (367 Miles).
Unless the train that MC makes runs over 200 KM per hour (meaning atleast under 3 hours of travel time), it would take a long time for Liz to be able to commute between the two cities.
Doesn't matter. She needs to only be able to take a few quests here or there to keep up her license and help Miyabi get his funds. Doing so over the weekend is more than sufficient. It's not like she needs to pick long-lasting quests.
In a world with monster, flying seems more reliable than a train. Its way harder to introduce tho, hmm. Or maybe if its underground train but its a ridiculous amount of work needed.
In ANY world, land travel is the safest. Water is filled with extremely dangerous animals with 3 dimensions of movements 100% of the time.
Air is relatively safe in some worlds (like ours), but it very susceptible to weather and dependent on a number of atmospheric factors that need to be solved. Furthermore, any failure is extremely dangerous and potentially fatal.
In a world with flying MONSTERS, air is extremely dangerous. There's nowhere you can hide, nowhere you can take cover. You can be attacked from any direction. The risk of failure (which is extremely dangerous, remember) is grown exponentially even with the best precautions. Any safety measures like parachute are utterly useless, as you would be a sitting duck.
Meanwhile, land has a lot of obstacles that can be used to hide or cover behind. It also is limited to mostly horizontal threats. It is not susceptible to most weather conditions and there is very low danger that comes with typical failure. If you trip or are sent 'flying', most of the time you're going to get up without much damage at all. Even if whatever keeps you 'standing' (aka. legs if you're on foot) will suddenly fail, unless it stops mid-way during high-speed movement, it's very likely you will survive. Even if it IS during high-speed movement, there are still quite good chances you will survive.
Or even just a personal motor vehicle. They only have horse-drawn carriage from what we saw so if he can make something that can go much faster and for greater distances it would be very appealing. A car or truck can be bought and used by wealthy individuals whereas a train requires a lot more investment in infrastructure, personnel, and only makes sense if there is a lot of people and goods that need to be regularly moved.
This isn't as good an idea as it seems. It would require making the roads before it could serve any purpose. After all, you cannot move fast on a land-moving vehicle when the ground is unstable. The speed would not be much higher than is the case for a coach/carriage. Meanwhile, there are numerous issues.
If you have the vehicle run on magic, you need...magic. The girl has little magic so she would run out extremely fast. If she'd use magic for transportation, she wouldn't be able to defend herself from monsters.
If you do NOT use magic, then you still need fuel. It would be difficult to find fuel that could last the entire trip on a vehicle small enough to allow them actually make the trip based on the conditions on the road.
And when they would make roads? There would be constant risk of crashing into people. Remember, they couldn't make people aware to keep on the side of the road. The concept of a fast, motorized vehicle doesn't exist there, and no long-distance logistics are properly written into law.
And what about monsters? Even on Earth, a deer coming onto the road is extremely dangerous for a modern car. Personal transportation in a world of monsters that WANT to get in your way and WANT to kill you would be a royal nightmare. There's almost no chance you wouldn't have an accident within the first two or three months of using it on a distance like that simply due to large monster suddenly jumping out at you.
Trains don't have any of these issues. They are massive, since they are used for large numbers of people and goods. Keeping fuel onboard is not a problem at all. Simple fuel can also be used easily, whereas it would be hard on a car-sized vehicle (since simple fuel is not very efficient).
Since tracks do NOT help with anyone moving besides the train, no one would get along them. They could cross them, but not block them.
Since trains are extremely heavy, and this is a world of magic, I imagine even a face-on collision with a large monster would pose very little threat. Rather, most monsters that are dangerous for travelers would simply explode from the force of the crash, and with magical barriers, the train could come out of it with little more than some shakes, maybe some smaller dents. A proper design could actually turn it into a deadly weapon, too.
Bandits are indeed a potential problem, but there are ways that it can be solved. For example, the tracks could have some minor electric enchantment on them that will stop working if the tracks are broken. And if they are broken, the train would stop within a certain distance (possibly anywhere on the tracks). Also, some emergency wheels that can just go on the bare ground could be made to prevent derailment, maybe even allow getting back on tracks on the other side of the breakage.
