MEXICO CITY -- Julieta Lopez was riding the 128 bus to her cleaning job in a ritzy Mexico City neighborhood when she felt the chill of pistols pressed against her cheek and forehead.
A gang of teenagers took everything from the 45-year-old maid and everyone else on board the pesera, or microbus, making passengers throw money and valuables into a bag of sand to conceal the loot.
"You know the robbers come often, but you get on and say, 'I hope they don't come today,"' said Lopez, who still takes the bus 128 six days a week, despite being robbed four times at gun- or knife-point.
So rampant are these robberies that authorities last week equipped 25 peseras with panic buttons.
When the driver pushes the red button, a satellite signal leads police to the bus. It also activates a hidden camera and microphone to give authorities a glimpse of what's happening on board.
Another 25 microbuses with panic buttons should rumble into service this month, but for now nearly all of those equipped with the buttons are plying the congested streets along Route 128, which runs west and passes near the airport.
Those carrying panic buttons are indistinguishable from the city's other 28,000 green-and-white minibuses, which cost as little as 20 cents to ride. Some have cracked windshields, are splattered with graffiti and are missing mufflers or mirrors.
28,000 buttons"This will improve things. The criminals won't know which buses are being watched by satellites and which aren't," said Luis Hernandez, a 30-year-old insurance adjuster who was riding a 128 bus home.
Police chief Marcelo Ebrard said officials will pay private security firms to install panic buttons aboard hundreds of the city's 28,000 buses in coming months.
But he said the cost -- up to $1,100 per bus -- means fewer panic buttons than officials would like.
Mexico City's attorney general, Bernardo Batiz, said panic buttons could also be installed in some of the city's 100,000 Volkswagen Beetle taxis, where hijackings are even more common than on buses.
But corruption could be a problem.
David, a driver whose Route 128 bus doesn't have a panic button, said police often take bribes to protect the bus-robbing gangs known as "ratas," or rats.
"It's a good idea, but how long is it going to last?" asked the 28-year-old, who said hijackers might come after him if he gave his last name. "For a few weeks everyone will talk about the buttons. After that the police will help the rats again."
Others say bus drivers often abet the robbers for a piece of the take.
The button should be accessible to all, like the emergency brake on a subway train, said Jasmine Villanueva, a 28-year-old accountant who stopped taking the bus after her father was robbed on one last year.
"If we have to trust the bus drivers, we're all in trouble," she said.
Bus crime has long been common in Mexico City, but last month came two especially horrifying hijackings within two days, in which gangs even raped some of the women on board.
The cases prompted a citywide crackdown. Over the next week, hundreds of police officers patrolled major streets after dark, searching nearly all buses running late-night routes. Authorities eventually captured a gang of alleged hijackers, but that did little to make most riders feel safer.
"From the instant I get on, I'm scared every minute," college student Daniela Moreno, 21, said while waiting for the bus. "Everyone rides the bus, but no one feels safe."
On Wednesday, city officials drove journalists around the city on a bus with a panic button and pressed it to test police response. A dozen patrol cars surrounded the vehicle in minutes, unleashing a swarm of officers who insisted they thought they were responding to a real emergency.
But other emergency-response programs have a dubious history here. Earlier this year, authorities installed dozens of panic buttons on sidewalks and along pedestrian malls near the historic downtown area that were supposed to connect to an emergency operator.
People complained of waiting several minutes for an answer.