human
Why are manhole covers in the middle of the road and not on the sidewalk?
gpt
Manhole covers are typically located in the middle of the road for several reasons:

1. Accessibility: Manholes provide access to underground utilities such as sewage systems, water pipes, or electrical conduits. Placing them in the middle of the road often allows for more direct and straightforward routing of these systems.

2. Safety: If manholes were located on sidewalks, they might pose a risk to pedestrians, especially those with visual impairments. In contrast, road vehicles are better equipped to safely pass over manholes.

3. Infrastructure layout: The underlying infrastructure that manholes access, such as sewer lines and water mains, often runs beneath the roadways, following the same general path. Therefore, placing manholes in the road provides the most direct access.

4. Construction and maintenance: When maintenance or construction work needs to be performed, it's often safer and less disruptive to divert or control road traffic than to block pedestrian walkways.

Despite these reasons, you might still find some manholes on sidewalks or other areas depending on the specific layout and needs of the underground infrastructure. The placement is ultimately determined by utility companies and city planners based on what is most practical and safe.
human
Interesting. Could you provide more facts on manholes?
gpt
Sure, here are some facts on manholes:

A manhole (also called a utility hole, maintenance hole, or sewer hole) is an opening to a confined space such as a shaft, utility vault, or large vessel.
Manholes are often used as an access point for an underground public utility, allowing inspection, maintenance, and system upgrades.
The majority of underground services have manholes, including water, sewers, telephone, electricity, storm drains, district heating, and gas.
Manhole covers are flat plugs designed to prevent accidental or unauthorized access to the manhole. They are traditionally made of metal, but may be constructed from precast concrete, glass reinforced plastic or other composite materials.
Manholes usually have metal or polypropylene steps on the wall to make it easier to get into the manhole.
Manholes are usually found in urban areas, in streets and sometimes under sidewalks. They are usually circular to stop the manhole cover from falling into the hole.
Manholes can be classified based on their depth as shallow, normal or deep. Shallow manholes have a depth ranging between 75 to 90 cm, normal manholes have a depth of 150 cm, and deep manholes have a depth greater than 150 cm.
Manholes can also be classified based on their material as plastic, precast concrete or fiberglass. Plastic and fiberglass manholes are commonly used where corrosion by sewer gas or infiltration and exfiltration are a concern.