TOKYO – Japanese police intend to embark upon a dedicated effort to pressure so-called “groping” websites to close. The move — aimed at about 100 known online forums and advice sites — comes amid the deployment of additional law-enforcement officers on congested commuter rail lines as a deterrent to an escalation in non-violent assaults on female passengers.In August, the National Police Force announced a cooperative effort with railway operators to protect women from unwanted attention. The plan includes installation of additional security cameras and introduction of more female-only passenger cars during the busiest hours of the day.

The groping problem is exacerbated by websites that point men in the direction of the most likely times and lines on which to cop a feel. The number of complaints from offended women has skyrocketed in recent years, and some 1,800 arrests occur annually. Police speculate the number of attacks may be orders of magnitude higher, as many victims are too embarrassed to report an assault.

Difficulty in proving allegations has compounded authorities’ frustration. High-profile cases frequently are overturned on appeal. In 2008, a 63-year-old professor at the National Defense College was acquitted by the Supreme Court on appeal in a case involving the molestation of a 16-year-old female railway passenger. The passenger’s testimony was the only evidence against the man, whom a lower court had sentenced to 22 months in prison for the 2006 escapade.

Other prosecutions have been successful. Earlier this year, a 23-year-old man confessed to fondling a high-school student on a train. He told police he had chosen to use a particular technique on a particular line at a particular time because the railway received high marks on a Web-based forum devoted to groping.