Firstly, trains should be split into 2 classes:
Passenger trains would be used predominantly for transportation and have a significantly lower chest percentage (someone similar to the Zep). On the other hand, the speed of this train could be increased to much higher, such as 50m/s, with acceleration being applied here for the train to speed up gradually. This will help increase the number of railways worldwide, shifting the transport balance from zeps to trains.
Freight trains would become goods trains, transporting large amounts of items over a large area. This should be done while reducing its speed to around 20m/s (slightly faster than trucks). On the flip side, there could be an increased percentage of chests while increasing the length minimum of such trains to around 50 blocks. This prevents train chests from being clustered around the front and allows trains to look more like actual trains. These trains could include acceleration, too, because it looks weird for trains to jump-start from stationary.
Secondly, there should be a rail banning overground railways without substantial infrastructure, such as viaducts/bridges. This will help prevent the cross-continent/ocean railways from appearing.
Thirdly, make it possible to walk around a train. For example, increase the interval gap where the train moves. A possible interval would be around 1.5 s-2 s. This will help reduce lag increasing functionality for trains, especially the passenger variant. In addition, this will allow the looting of slow-moving trains, as commonly seen irl.
I hope you guys will consider the suggestions I have. Although it is not applicable to many players, I feel these changes would still help in shifting the balance from zeps to other modes such as trains.