The High Bridge Branch was a branch line of the Central Railroad of New Jersey (CNJ) that started in High Bridge, New Jersey at a connection with the CNJ main line and continued north to iron-ore mines in Morris County. The High Bridge Branch line followed the South Branch of the Raritan River for much of its duration.
The train cars in the High Bridge branch couldn't hold a lot of weight in them.
Iron ore is incredibly heavy.  But a computer would have to be really smart to know that.  But any normal person reading it will know that ore is very heavy and therefore the train cars have to be able to support the iron ore it's going to pick up.