Latent heat of vaporization means huge quantities of LNG stay liquid for plenty long enough to get a flaming tsunami. Your not going to end up with petroleum contamination, but in terms of loss of life their about equally dangerous.

Anyway rail transport of oil through populated areas is also a major risk. Which is why it’s also banned in some places.

If you had a tsunami of LNG it would be more likely to freeze you than burn you. However the latent heat of vaporization for LNG is very low, it will vaporize quickly as it spreads out, unlike crude oil. You certainly won't get a flaming tsunami - you can actually extinguish a flame in LNG.

Transport of oil through populated areas is quite common. Local governments that have restricted its transport are welcome to do the same for LNG.

Latent heat of vaporization of LNG is 512 kJ/kg vs 2257 kJ/kg for water. Which is basically irrelevant when your talking into the million’s of kg of the stuff.

Do some math and even just a single 35,000 gallon tanker load is going to flow around like a liquid for quite some time.

3 kg of dry dirt at 20 deg C has enough energy to vaporize a kg of LNG (it takes slightly less concrete). Assuming on the timescales involved it can come into thermal contact with the top inch of soil, all the LNG from that tanker should dissipate once it spreads over a surface of 3000 m^2, or about 60% of the area a football field. It vaporizes faster when you take into account other sources of heat like the air, and way faster if you light it on fire. At most it'll be on the ground for a few minutes, but for a real spill it could be just seconds.

Sure, if it ended up in a nice flat cornfield somewhere then no problem, but the urban landscape is designed to channel ran. Thus it’s more a question of dispersal not duration.

Let’s say 10 tanker cars so 350,000 gallons or 560,000kg are spread down a water channel at the side of a street at 15mph. At 4 minutes their already covering 1 mile which easily takes them out of most towns making longer durations largely meaningless. If the channel is V shaped with a depth of 2 feet and a width of 10 feet. That only adds up to ~4,5000 square meters, and by your calculations most of it should still be there.

It doesn’t last as long if it’s on fire, but there’s going to be an air gap of unmixed natural gas over a likely several feel thick channel of LNG. So even then it’s going to take a while to burn off meanwhile the wave of fire is destroying everything around it.

10 tanker cars all instantaneously emptying directly into a 2 feet deep and 10 feet wide v shaped channel at the same point is not at all realistic. For starters, your V shaped channel is perfectly full when the LNG is spread out over a mile - over the preceding 4 minutes the LNG was spilling over the side of the channel onto the surrounding flat ground, dramatically increasing the amount of ambient heat it would have absorbed.

In a real scenario, the cars are going to be spread out over an area, their ruptures will be relatively small orifices that the fluid must flow through, it's going to spill out rapidly in all directions from that point, any area where a train is passing through is going to be decently wide and flat, worst case scenario probably a 50 foot wide street.

You can look up pictures of derailed tanker cars, for example [0], and see the area where the liquid spills over. By the time the contents of a tanker car have spread over an area of 1 acre, the fluid is only 1in deep, even if none of it vaporizes it's limited in how far it can meaningfully spread. The spill of a cryogenic fluid will by necessity cover less area. As you can see, the spill of 322,000 gallons of flammable liquid affects an area comparable to that threatened by the derailed train cars themselves. That fire lasted 36 hours, wouldn't it be great if all the fuel evaporated in 36 minutes?

[0] https://www.progressiverailroading.com/federal_legislation_r...

That sounds more like an argument against allowing rail transport of petroleum rather than an argument for allowing rail transport of LNG.

It very well could be if you don't feel the benefits outweigh the risks. But it's dumb to be fine with rail transport of petroleum and not LNG.