From #openttdcoop wiki
A formula to calculate the coopish-ness of a OpenTTD game:
The lower the index, the higher the coopish-ness of the game. For games with trains using different lengths and speeds calculate the averages first.
On IRC you can use our bot JJ to calculate a CI for you using the following command:
@CI <mapwidth> <maplength> <number of trains> <trainlength> <speed>