You don't need the permission of passersby on the street. However, each person you interview should have given you their consent. People can give their consent by signing a form (example here) or by giving their consent on camera.

For the purposes of your project, it is most efficient to get consent recorded on camera. Here's how to do it.

Explain briefly the purpose of your filming project and what you want to do with the footage. You could say something like this:

"I am filming the project called ... [name of your project] to spread the word online about young people involved in community projects. I want to interview some people who are involved in the community project. Is it ok if I interview you?"

If he/she says yes, then get them to say this on camera:

Vlogger: "Please say your name."

Interview Subject: "My name is ...."

Vlogger:  "Please repeat, I consent to be interviewed for this project."

Interview Subject: "I consent to be interviewed for this project."

Make sure you save the evidence on film or on paper. This legally allows you to use interviews in your video project.

For more information on legal matters to do with filming, see this excellent page on release forms by 4docs.