Part of the problem is that while the 2011 law bars all the violations listed above, a separate statute that would establish penalties has repeatedly been delayed. So even if a cop were inclined to stop a driver for riding without a helmet, he couldn't write out a ticket because there's no rule that says how much the fine should be.

Experts say motorcyclists' sense of impunity has helped drive an even more troubling trend, that of the vehicles being used to commit crimes.

Armed robbers on motorcycles regularly prey on helpless motorists caught in bumper-to-bumper gridlock, where police patrol cars have no way to respond to a call.

"I'm in a traffic jam and they go like this on the window," said Alvarez, imitating the sound of a gun butt tapping on glass. "What else can I do? I roll down the window. 'Give me everything you have.' Here you go, brother. I'm not going to risk my life for material belongings."

Motorcycle gangs have spread and made a tradition of forming boozy caravans after the funeral of one of their own, deliberately jamming up traffic to demand "contributions" from motorists or rob them outright.

Last month, in a case that shocked even calloused Caracas residents for its audacity, as many as 40 bikers in one such procession relieved dozens of drivers of their wallets, purses, laptops and cellphones on a main road in the suburb of Macaracuay.

Newspaper crime pages are full of accounts of murders carried out from bike-back. And earlier this year a 17-year-old Caracas girl was raped by two men after the mototaxi driver she hired delivered her to her attackers.

There are some signs that President Nicolas Maduro is serious about tackling the problem. He speaks much more frequently than his predecessor, the late Hugo Chavez, about combatting crime.

"The full weight of the law will fall upon anyone who does not adjust to the rules," Interior and Justice Minister Miguel Rodriguez Torres said last month.

Authorities said recently they are negotiating with motorcycle clubs on the language of the regulations.

Some of the gangs have powerful political ties, having been encouraged by the government to organize after a failed coup attempt against Chavez in 2002.

When Chavez died this March, one such gang roughed up students who had been protesting near the Supreme Court. A month later, around election day, militants on motorcycles threw a firebomb into a political party office and vandalized a bakery they said belonged to an opposition supporter.

"When you feed little monsters and those monsters grow, they take on a life of their own," Marmol Garcia said. "And perhaps ... the anarchy of the motorcycle union is a monster that today has great power and will cause great concern in the political establishment as it tries to rein them in."

For a case study Venezuela need look no further than neighboring Colombia, where motorcycles were once synonymous with drug cartel assassins. Authorities there have made significant strides by enforcing registration rules and helmet and reflective vest requirements, outlawing mototaxis and letting mayors prohibit motorcycle passengers during times of unrest.

There are about 275,000 registered motorcycles in Venezuela today, according to the most recent census in this nation of 28 million, though the true number likely exceeds 800,000, El Universal newspaper recently reported.

Yet the motorcycle boom has also made life easier for many and allowed countless Venezuelans to earn an honest living as drivers, couriers and so on.

Mototaxis, once essentially unheard of, await customers on every other street corner in the downtown business district. At rush hour everyone from working-class laborers to lawyers in business suits can be seen hopping on the back of motorcycles.

Henry Frias, a 35-year-old bank worker, frequently takes mototaxis to cut what would be an hour-and-a-half, 5-mile (8-kilometer) morning commute by bus, to just 15 minutes.

"I have to be there by 8:00 a.m., but with the stoplights and the traffic it's impossible," Frias said recently, dressed in gray slacks and a pressed white dress shirt. "It has its dangers because with a mototaxi you're often at risk of suffering any kind of accident ... but this is the surest way to arrive on time."