[PRCo] Green boxes

[Dietrich, Robert J.]

Things have been quiet for a couple days folks, I'm surprised.  Am I
imagining things or did the city place big green boxes on selected
street corners in the winter months?  As I recall they contained rock
salt for getting cars out of a jam.  If I'm on the right track so far
then what were those boxes called?

I do have a SHJ connection to this question.  What is in the green box
in this picture http://mywebpages.comcast.net/bdietrich/outback.htm? 

Thanks.

Bob