By default all industry cargo got a weight of 1200 per unit - that is 1200 kg per cubic metre.
Some mods already change that, like
https://steamcommunity.com/sharedfiles/ ... 1951335527
https://www.transportfever.net/filebase ... ndustries/
Examples:
Planks are 528 kg per m³
Plastic 1250 kg per m³
Iron ore 2400 kg per m³
Coal 1350 kg per m³
Steel 7900 kg per m³
Tools 2950 kg per m³
These values acknowledge that not all goods are solid cubes, some got a lot of air gaps inbetween the single items, like one cubic metre of tools is including packaging and air gaps - not equivalent to a solid block of steel.
The heavier cargo types combined with 4x cargo capacity makes trains realistically heavy.
This makes it necessary to carefully plan the tracks.
And the use of old english locomotivces in early game (more experience in engineering, more power, more speed) - as it was done in reality as well also in the middle of Europe (so that's not cheating).
I also have to use a mod that increases the amount of cargo the train station platforms can carry.
For Tpf1 there was a mod that got a dedicated table for replacing values - not just a generic script.
It was
https://www.transportfever.net/filebase ... entry/2872
Its main purpose was not to "just" change the cargo capacity or "just" change the cargo weights - it added two new parameters:
maxWeight and maxVolume
So a truck could have a maxWeight of 40 tons but also a maxVolume of let's say 31 m³
So it was only able to carry a low amount of heavy goods like steel but a much higher amount of goods like plastic.
Hopefully a mechanic like this will also come back to Tpf2 with a new version of that mod.
Notes: 
IMPORTANT: Minimum game version for updated trucks: Version 28772 (May 6, 2020)
