EXAMINE WHY A MANHOLE COVER JUMPED OUT OF ITS CASTING
THE TIDDLY WINK EFFECT
Review of the Event
A vehicle was driving along a main road when it struck an open sewer manhole, lost control and crashed into a tree. The road had been re-surfaced a few months prior. The sewer manhole cover had been raised to match the new roadway surface with a casting riser. After the re-surfacing the manhole cover began banging whenever a vehicle drove over it. A few weeks prior to the crash a neighbor had seen the manhole cover pop out of the casting and roll away. The neighbor found the cover and replaced it . As cars drove over the manhole cover it banged until one night the cover either broke and fell into the manhole, rolled away or someone took it.
Tire rolling over properly seated manhole cover at 30 mph
Tire rolling over improperly seated manhole cover at 30 mph
After the Manhole cover has been given the initial rotation because of the tire rolling over it, it is free to continue to rotate and can slide or pop out of the casting].
Last update: 05/15/2019