I see "broken" as a binary state. If the numbers are broken, you can't break them more, no?
By the way, I changed some other values (engine_type) in the meantime, please do not overwrite these... but that's a problem of using svn the right way, not your changes.
edit: I started playing and immediately some flaws are apparent... not just with your balancing! This is starting to be a rather complex problem. Let's see:
Start in 1930, now I am finishing 1930.
I "kinda" overdid it with field productivity. Grain farms are far more productive than is the actual need, at least as far as I can observe. Good for me, at least somewhere I can pump money steadily.
Compared to my memories, quite a few vehicles feel underpowered.
Ironically enough, there are not enough buses to meet the speed limit when starting game! I get zero bonus for 50 kmh, but most vehicles can do only up to 45, and even poorer model is introduced. The PC-ed bus with 58 kmh is all nice and should make insane money compared to the rest, but is horribly weak and can't drive at full speed… it could be easily overtaken by the slower models!
So I have real trouble making any money with buses, I use the most economical one and the fastest one and they make more or less same money. But the other models have even worse parameters...
Clearly the speedbonus table is too optimistic :

Let's see about that >:(
Question: how do you decide if a vehicle is "productive"? As I see it, it should make profit at the time it is removed from production, since it can be bought even then. It doesn't look that way with all the costly buses...?
Argh, now I am really starting to be frustrated. I can make lots of money on grain and flour :-/ Coal pays poorly. Passengers are hell.
So, I stayed up until 3:20 am and kept feverishly punching fast-forward button to see what comes next… never more!
The speed bonus is largely disconnected from reality, so obviously that needs to be changed. Should I look into that, or do you want to perform some C# black magic punishment on it yourself?
road=1911,21,1928,50,2001,82,2032,85
The entry "1928,50" obviously created most of my problems.
I had only one train line, so most of the comments are not related to it. Everything is about road transport.
One more idea... maybe I am overestimating the importance of speed bonus. It certainly does not matter with some cargoes. But I see most vehicles always under it! That's what I can't get over.