Take a look at second post on the following thread which describes passenger-km (https://www.energycommunity.org/default.asp?action=9&fid=22&TID=3787). There is a link to a very useful resource which explains some of the terminology commonly used in transport analysis.

Also note that passenger-km is just one way for estimating energy demand for the transport sector. You may want to use another method or units based on the data you have available. You can change the units used in the Activity Level and Final Energy Intensity variables, or add custom units in the Units manager, accessed through General --> Units.

Thanks,

Emily