- Most of the world's tunnels are considered safe for drivers, but a few are still decaying rapidly.
- The world's worst tunnels are often plagued by leaking walls, corroding infrastructure, and collapsing or uneven roads.
- We've rounded up six tunnel systems that are in desperate need of repair - including two in New York City.
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Elon Musk may have moonshot dreams of building high-speed loops that whiz passengers from city to city, but the world's tunnels are a far cry from this vision.
Read more: 7 of the most dangerous roads in the world
Rather than serving as oases from traffic, many modern tunnels suffer from congestion and corroding infrastructure. A select few are even becoming dangerous, posing a threat to the daily operations of thousands - in some cases, millions - of residents.
Here are six tunnels that are in such desperate need of repair, they might easily be considered the world's worst.