Why are there liquid nitrogen tanks in the median?

Since moving to Dallas, I’ve seen two or three nitrogen tanks in the median of streets connected to some box. Below is a picture of the one near my house. I mentioned it on Facebook a few weeks ago, and today my brother said he saw one in Tyler where he lives. I don’t recall ever seeing any until a few months ago. What is their purpose?

http://img834.imageshack.us/img834/3510/08161806.jpg

Underground wire/cable maintenance, most likely: Google Answers: Liquid nitrogen into sewers - why?

Interesting. How long do they typically get left there?

Morbid soul that I am, my immediate thought was - has anyone ever run into one in a traffic accident? Anything happen?

umm… ever seen Terminator 2?

Only a T-1000. But not for long…

ETA [Homer Simpson] Oooh! jz78817 beat me to it! [/Homer Simpson]