Such muggings on public transportation, at public beaches and in popular tourist areas are on the rise in Rio de Janeiro, eroding the strides the city had made in security in recent years as it geared up to host seven World Cup games and the 2016 Olympics.
The phenomenon also dovetails with a general rise in non-transit related muggings and robberies. In the first three months of the year, the number of muggings reported in the city's marquee Copacabana neighborhood rose nearly 60 percent from the same period a year earlier.
Paulo Storani, a security expert who spent nearly 30 years on Rio's police force, said at least half of the 12 World Cup host cities have experienced a recent rise in violent crime. He attributed the increases to a feeling of impunity.
"People do not recognize the authority of government officials, and as a result criminals are more at ease to commit their crimes because they feel they will not be arrested or punished," Storani said.
The U.S. State Department has warned its citizens traveling to Brazil of "frequent" robberies on city buses, in banks and at ATMs and recommended against resisting thieves. British and German authorities have made similar recommendations.
The situation in Rio's public transit has gotten so bad that state lawmakers have proposed the creation of a specialized police battalion for the city's fleet of nearly 9,000 buses. Rio Gov. Luiz Fernando Pezao reportedly favors the proposal but it needs to clear several more legislative hurdles.
Pezao characterized the city's fight against criminality as "a war."
Rio state's top security official, Jose Mariano Beltrame, has responded to the spike in crime by beefing up the number of officers who will be on duty during the June 12-July 13 World Cup by around 20 percent.
But with little concrete improvement so far, Rio residents are turning to the Internet for help. A website called "Where I Was Robbed" allows users to pinpoint the exact location of muggings, carjackings and other crimes in the city. Users of the site have tagged more than 360 mass muggings on public transit since the beginning of the year.
It's not just robberies that have made public transportation in Rio dangerous.
A year ago, the gang rape of an American student aboard a public transit van made headlines around the world. The student and her French boyfriend hailed the van in Copacabana. The van's driver, money-taker and another man soon forced the other passengers to disembark, tied up the Frenchman and subjected the woman to what a police investigator described as an all-night-long "party of evil," raping her repeatedly.
Although investigators quickly tracked down those responsible, it emerged that police had failed to follow up on earlier reports by Brazilian women who were raped by the trio under similar circumstances.
The issue of sexual violence in public transport captured headlines again earlier this year, this time in Sao Paulo, which is hosting the World Cup's opening match. Authorities there detained several men for allegedly accosting women on subways and buses, sometimes filming them with cellphones and posting the videos of the molestations on social media.
Dilma Rousseff, Brazil's first woman president, said on Twitter that such acts "shame our society."
While it's unclear if the rate of sexual assault has increased in the past year, the high-profile attacks have fueled the widespread perception that using public transportation is dangerous.
Sao Paulo's flurry of public transit crimes coincides with an increase in robberies, with the number of monthly reports up nearly 50 percent.
In Rio, the crime spike comes despite a "pacification" program launched in 2008 that brought police outposts to "favela" slums where the state had long been absent. The campaign initially saw crime fall, and Rio residents began taking walks after dark again.
But the resurgence in crime is driving many back into a siege mentality and fueling fears of problems when an estimated 600,000 foreigners descend on Brazil for the World Cup.
Joe Biundini, president of the security company FAM International, called transportation in Rio a major concern.
"The risk of kidnappings and assaults inside a moving vehicle is huge," said Biundini, whose firm is providing security for VIP clients attending World Cup matches in Rio and Sao Paulo.
by JENNY BARCHFIELD