Passenger coaches have a "ride quality" attribute

[Stumo]

I'm now getting round to implementing

http://www.tt-forums.net/viewtopic.php?p=223925

only I've had a look through the code and I'm not sure what parts of the vehicle code I'm allowed to change without breaking much and what I'm not. Is there any guidance for what can be changed?

If someone who understanda the vehicle code well would be able to take me to one side and talk me through stuff at some point, it'd be appreciated. I'm on IRC as Stumo, but not always there (and don't always remember to use my away message) so don't think I'm ignoring you if I don't reply.