The City Council is investigating ways to reduce sexual harassment and assault in the subways after hearing testimony Thursday from NYPD officials who say there's been a four percent increase in the number of complaints filed over the past year.

The chief of the Transit Bureau says it's most common on the number 4, 5, and 6 lines in Manhattan and occurs primarily during the morning and evening rush hours.

"Last year to this year complaints are up four percent from last year -- 564 last year, 587 this year. Sixty three percent are sexual abuse, 35 percent are public lewdness," said NYPD Transit Bureau Chief James Hall.

Many women NY1 spoke with say they've come to expect sexual harassment as an evil by product of riding the subway.

"Sometimes when it's really crowded like now, a guy will come hold the bar and push against you. Usually, I just quickly move," said one female subway rider.

"I always watch my personal space. I try not to disturb others and if I see somebody who doesn't look right or acting inappropriate I move away," said another female subway rider.

The NYPD believes many women aren't reporting sex offenses on the subway either because they're ashamed or they think with more than five million people riding each day, finding a suspect is like finding that proverbial needle in a haystack.

"There is a clamor for more enforcement, more prevention, for this type of criminal behavior on our subways," said City Councilman John Liu.

Since 2006, police have targeted subway crimes using undercover surveillance and coordinating with various divisions within the department. Police say the most important weapon in their fight is getting women to report crimes.

Authorities say if you're harassed on the subway you should report the incident immediately and if you can, snap a picture.

Police say cell phone photos have been instrumental in catching suspects.