In Demand module, the default units for length have not been incorporated in Activity level, although there are many units in unit Database.
I did not noticed it until one of my students came across the idea for Road lighting by solar, for which expansion of road networks (in km) would have been the driving factor. In same note, then i came to realize, such as in industrial sector, where energy intensity for textiles and fabrics could be found in energy per meter.
This missing unit is no a big deal, but could be useful in certain limited cases so that one would not need to develop either a Other unit(which requires naming to be other than one in Unit database already) or a separate branch in key assumption or a separate user variable for intermediate calculation.

With Thanks,
Utsav

Charlie