MEXICO CITY  Body-to-body contact is inescapable on Mexico City’s crowded public transportation system. Get on a train or a bus during rush hour and a man in a business suit may have his arm resting against your shoulder, a woman toting a bulky shopping bag may have her back pressed against your flank, and a teenager listening to an iPod may tap his sneaker all over your newly shined left shoe.

But many women complain that not all the contact is incidental. Among the 22 million passengers who use the bus and subway system daily, women say, are lecherous men taking advantage of the cheek-to-jowl conditions to leer and grope and then quietly disappear.

“There are good men in Mexico, but they’re not the ones on public transport,” said Mariana Vasquez, 30, who waited to board a bus recently on her way to a job interview at a law firm. “They try to touch you. They don’t give you a seat. Where are the gentlemen?”

One place they are not is on new women-only buses that Mexico City began running in January to reduce the harassment. With pink placards and insistent drivers who growl at any man who tries to step aboard, the buses are quickly becoming a hit among women.