UP TO three-quarters of teenagers who live in Melbourne's west believe gangs are a presence in their neighbourhoods and a third have had an encounter with them, according to a two-year study on community safety.

Researchers surveyed 500 people aged 15 to 19 in the Brimbank council area to compile the findings released today in The Age. The participants were drawn from 20 western suburbs including Sunshine, St Albans, Deer Park, Keilor and Taylors Lakes.

The conduct they identified with gangs ranged from anti-social behaviour in public places - commonly youths being loud and ''eyeballing'' others - to more intimidating fights and bashings.

The study, commissioned by Victoria Police and conducted independently by Victoria University, also found half the survey participants said they knew of other young people who carried weapons ''regularly''.

Dislodged supermarket trolley poles, bats, knives, machetes and sometimes guns were identified as weapons chosen by their peers. The participants said the desire to carry such weapons was linked primarily to the need to feel safe, protected or for self-defence.

About a quarter of those surveyed also acknowledged that they had carried weapons at some time, saying they did it primarily to ensure their personal safety. Males were twice as likely to have engaged in such activity.

Overall, only half the participants said they felt safe or extremely safe in their neighbourhoods. Train and bus stations were seen as among the least safe places to gather.

''There is a widespread perception among young people that there are street gangs in their area, yet the vast majority of group gathering in public places is not being done by young people whom we'd associate as being in 'gangs','' said Michelle Grossman, an author of the study.

A striking feature of the ethnically diverse urban landscape of Melbourne's west, Professor Grossman said, was the propensity of its younger residents to ''hang out'' in public - with 76 per cent of survey participants saying they often or sometimes engaged in this type of outing.

''Overwhelmingly, what we found was that young people tend to gather in cross-ethnic groups based on friendships, common interests and in order to feel safe in the local area. One of the common assumptions these young people reject is that youth congregate in ethnically based gangs with criminal intent.''

The study, which encouraged the youth to speak freely and guaranteed confidentiality, also sought participants' views of police. While 58 per cent said they felt safer when they saw officers on the street, just under half acknowledged young people in their area held negative views of police.

Furthermore, only half the participants said they trusted or completely trusted police.

Asked how police could develop better relationships with them, the youth emphasised better communication and conduct towards young people by street police.

''These findings are an indication to police that they could do more to work with young people to improve trust,'' co-author Jenny Sharples said.