Please refer https://github.com/teamhimeh/simutrans/blob/OTRP-distribute/documentation/OTRP_information_en.md about this project.
OTRP is a modified version of simutrans that some features are added to.
・Road vehicles take full advantage of two lanes. You can build and enjoy a 4-lane highway. ・For road, "citycars do not enter" and "avoid becoming cityroad" features are available. ・Regional mass build and land raise/lower tools are available. These tools are extremely useful for massive development.
The thread in Simutrans International Forum: https://forum.simutrans.com/index.php?topic=16659.0 Twitter hash tag : #OTRPatch