If the opening is triangular, the cover could fall through. I suspect though that the real reason is that people aren't triangular in cross section.An equilateral triangle also won't fall through. They had triangular manhole covers in Nashua NH although I don't know if any are left.
If it was in Japan it would be street art!
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Can you imagine tooling down the road in your bicycle and hitting that?If the opening is triangular, the cover could fall through. I suspect though that the real reason is that people aren't triangular in cross section.
On another note, Beijing, China is replacing cast iron manhole covers with plastic covers to deter theft. In 2004, almost a quarter million manhole covers were stolen in Beijing. And we worry about potholes.
On another note, Beijing, China is replacing cast iron manhole covers with plastic covers to deter theft. In 2004, almost a quarter million manhole covers were stolen in Beijing. And we worry about potholes.
That year, there were eight deaths in Beijing due to people falling into open manholes.Can you imagine tooling down the road in your bicycle and hitting that?
Remember the 'slotted' sewer grates back in the day? I do, hit one with my 10-speed. My buddy gave me no end of grief.
Then a couple of days later we were pedaling down a residential street talking back and forth and he slammed in the rear of a pristine '73 black Nova.
Over the roof and onto the hood. He was bruised and battered but OK. The Nova though was dented & scratched up.