eli5 why are manhole covers in the middle of the road and not on the sidewalk?
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The manholes you see in the middle of the road are generally to access stormwater pipes. Roads generally slope very slightly from the center to each side to drain rainwater to the kerb. The water then gets collected by a drain, and makes it’s way through a small pipe to the main pipe in the center. This arrangement ( main pipe in center with small pipes connecting to the drains at the edges) makes it easier to design the pipes with the optimal slopes to drain rainwater. Also, as you have drains on each side of the road, rainwater moves more quickly from the road surface.
Manholes that you see on the pavement /sidewalks are generally to access utilities such as electricity, gas, and communications cables, as there is no reason to put them in the road. Access to pavement areas is easier for obvious reasons.
Ultimately, access points to utilities and stormwater drains are placed based on both easy access for maintenance and design / construction constraints.
Source: I’m a civil engineer
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