The 6 worst tunnels in the world have leaking walls and slippery roads - take a look

In 2017, Travel and Leisure analyzed data from the Federal Highway Administration (FHWA) for nearly 700,000 bridges in the US. Their analysis awarded each bridge a "sufficiency rating" based on four FHWA categories: structural adequacy, safety, functionality, and whether it was used often by the public.

Boston's Storrow Drive, which includes the Storrow Drive Tunnel, received the worst rating possible: a zero on a scale of zero to 100. Over time, the tunnel's cracked beams, drooping ceiling, and leaks have mandated immediate repairs, but the entire structure will likely have to be rebuilt someday, an engineering professor told the Boston Globe.

The Hudson River tunnels in New York City aren't just old — they're also falling apart. After Superstorm Sandy flooded the tunnels with saltwater in 2012, the walls have begun to crumble and leak, and steel and electrical cables have corroded rapidly.

The tunnels' owner, Amtrak, has estimated that the tunnels have about a decade before at least one of them fails. New York legislators are still seeking federal funding for the renovations. At the moment, the tunnels are still considered safe, but time to repair them could be running out.

The Salang Tunnel in Afghanistan is plagued with hazards. Every day, around 10,000 to 20,000 vehicles pass through the tunnel and become exposed to structural defects like leaking walls and uneven or collapsing roads that cause cars to tilt to one side.

Because the tunnel is high up in the Hindu Kush mountains, it's also vulnerable to avalanches. In 2010, a series of more than a dozen avalanches near the tunnel killed at least 150 people and left thousands stranded in their cars.

Attempts to repair the tunnel have been stalled for many years due to political corruption, such as embezzlement and bribery.

Located in a suburban area of Moscow, the Lefortovo Tunnel is subject to fierce winter temperatures. When water leaks into the tunnel from the nearby Yauza River, it can freeze and turn into ice, which causes vehicles to slide.

Though drivers have more reason to fear accidents than a fatal crash, locals have nicknamed the structure "the tunnel of death."

The Lincoln Tunnel may not be the most congested road in America, but it's by far the most congested tunnel, according to a 2015 report from the American Highway Users Alliance. The report found that Lincoln Tunnel drivers endure 3.4 million hours of delays each year due to bottlenecks, or chokepoints where the number of cars exceeds the tunnel's capacity.

Traffic is made worse by construction on the Route 495 bridge, which has been deemed structurally deficient.

Like the other tunnels on this list, the Lincoln Tunnel is still considered safe for drivers — but that doesn't mean there aren't plenty of problems to fix.