Balken crude has more natural gas liquids (NLG's) in it than other crude and it is a light sweet crude not heavy crude, as the cars are transported the NGL's off gas from the crude and then you have gas in the vapor space of the car so in a derailment and a rupture of the
rail car the gas comes out 1st is very flammable and that is why the fire and then some explosions. Some of the producers are now looking at ways to remove the gas before loading the oil. Yes the oil producers knew but they failed to properly test and classify the oil and tell the railroads what the true make up of the oil was. This is the short on why Balken is more dangerous to ship. Crude oil without all the NLG's is very safe to transport and hard to set on fire.