Rio de Janeiro has another problem that could make the Summer Olympics a nightmare: traffic.

Though water conditions, Zika, and infrastructure are all worries leading up to the games, according to Paul Kiernan and Benjamin Parkin of The Wall Street Journal, Olympics organizers are increasingly worried about traffic.

According to the WSJ, Rio has 24% fewer residents than New York City, but 51% more private vehicles. Because Rio lacks a public-transportation system, citizens often drive, creating daily bumper-to-bumper traffic.

With an increase in visitors and many of the sporting venues in different parts of the city, the traffic could become worse. In fact, according to the WSJ, the traffic issues alone are already stressing out some members of the International Olympic Committee:

"Rio's traffic woes are so serious that some members of the International Olympic Committee are regretting their decision to award the Games to the city, a person familiar with the matter said."

As the WSJ notes, Rio has tried to prepare for the issue, with $1 billion in new roads and tunnels and Olympic-designated bus lanes, but there will still be issues.

For instance, while drivers who drive in the designated Olympics lanes could face a $450 fine, public prosecutors have fought the punishments as the lanes aren't written into federal traffic laws. Thus, it may be difficult to enforce the rules.

Similarly, as the WSJ reports, while the new Line 4 subway transit system is complete, it stops 8 miles short of the neighborhood of Barra da Tijuca, where half of the Olympic Village and many of the sports venues are located. Assuming that Line 4, which is still in testing, runs without problems, commuters will still have to catch a bus for the last 8 miles, adding to the congestion.

Rio is going to be highly congested for the next several weeks, and while the city seems to be working on solutions, expect at least a few stories of athletes and visitors getting stuck in gridlock traffic to and from the games.