CARACAS, Venezuela -- Ronald Alvarez was driving in chaotic, bumper-to-bumper traffic when he heard a throaty buzz and insistent "Beep! Beep! Beep!" approaching rapidly from behind.

Motorcyclists in Venezuela's capital are known for zipping between lanes and taking off side mirrors, either inadvertently or with malicious intent if they feel a driver hasn't left enough room. So Alvarez swerved to the side to open up space for this one, rear-ending a car that had slammed on its brakes in the process.

"It is the worst plague there is right now in Caracas," Alvarez fumed about the proliferation of motorcycles.

Alvarez's complaint is echoed by many residents of this capital of narrow streets, where the transportation infrastructure has been neglected for decades leading to traffic congestion so bad that it is almost always best navigated on motorcycle. A two-hour car drive to work can take less than half an hour on the back of a bike.

The two-wheel invasion began about a decade ago with the arrival of Chinese-made motorcycles that sell for just a few hundred dollars, and has since exploded, causing Caracas residents to rant at the locust-like swarms of motorcycles that blow through red lights and ignore one-way traffic signs with impunity, becoming a serious public health and safety issue.

Gangs of armed, two-wheeled political shock troops backed by the government terrorize voters and break up opposition protests. Motorcycles are also favored by robbers and hit-men, and are involved in 90 percent of violent crimes in this murderous city, according to an estimate by a prominent criminologist.

In 2011 the government finally passed a law that was supposed to help crack down on the lawlessness, but nearly two years later there's practically zero enforcement and people say the problem is only getting worse. For many the motorcycle has become a potent symbol of anarchy and ungovernability in a troubled nation.

"For me, the problem of motorcyclists has become a matter of public health," said Fermin Marmol Garcia, a criminologist who reached the 90 percent figure on motorcycles' involvement in violent crime by analyzing data from the government and NGOs. "It's no longer just a crime issue, a violence issue. It's a matter of public health."

Venezuela is the world's third-worst country for motor vehicle-related deaths with 37.2 per 100,000 inhabitants, according to a World Health Organization global road safety study published this year. Only the Dominican Republic and Thailand scored worse.

It's not clear how many of those involved motorcycles. But news of accidents are a constant on the radio, and one recent report said the more than a dozen hospitals in the capital treat at least 100 motorcycle injuries a week - apiece.

Spend an hour or so on the streets of Caracas, and you might see every conceivable traffic rule broken.

Streams of up to 50 bikes zoom between lanes of motionless cars. Dozens park on the sidewalk, blocking pedestrians' passage. Families of four ride a single motorcycle. Bikers mass under overpasses during storms, choking off traffic.

"It's like people transform when they get on a motorcycle," said taxi driver Samuel Tarazon, who last year watched one flatten an elderly man in a crosswalk. "It's such a violent manner of driving."

Police largely look the other way and some say they are among the worst offenders. Many government motorcycles circulate without license plates and are apparently not even registered.