In New York, sidewalks are typically laid in large hunks, say 20 x 30 all at 
one pour, each section separated from the other by that tubular stuff, I guess 
for expansion and contraction. 
 
But, within each larger pour, the concrete is invariably scored to produce 
imitation "flags" of about 5' x 5'.  I dimly recall that the 5' x 5' scoring is 
a city requirement, but what is the ultimate thinking behind it?   Cracks seem 
to ignore the score lines, frequently passing through them without deviation. 
The scoring is too shallow to concentrate run-off. 
 
Christopher 



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