"If people aren't expecting you to be there, then you're somehow not part of their reality," Scarlett told Metro, describing the experience as both "thrilling" and "terrifying".
The surreal experiment was captured by cameras hidden throughout the van, watched in the back by hidden crew members from Scarlett's new project Under the Skin.
Loosely based in the sci-fi novel of the same name, it follows an alien disguised as an attractive woman who prowls Glasgow looking for male prey to entice and eat. And to bring realism to the film, director Jonathan Glazer decide to send his leading lady out to interact with real passers-by.
It's no surprise that Scarlett so enjoyed the experience. "I see some of the young actors and young celebrities today desperately trying to fit back into society, which I totally understand," the 29-year-old told the newspaper.
"But really, once you accept your fate as someone who's a recognisable person, who's no longer anonymous, I think you have a much easier time fitting in than if you are constantly trying to be 'normal'."
Scarlett is understandably protective of her private life – she has yet to confirm reports that she is expecting her first baby with French fiancé Romain Dauriac.
"The trappings of this job mean I always feel like I'm protecting not just my personal life but my family, my partner, my lifestyle, my address everything," she said.
"Several years ago I had that whole awful hacking incident" – nude selfies she sent to then-husband Ryan Reynolds were intercepted and posted online – "which made me feel so paranoid. But I am trying not to let it affect me."
Private though she might be, things couldn't be going better for the star. Her stellar film career continues to thrive – she has four movies scheduled for release in 2014 - and away from the spotlight she is happily settled with 31-year-old Romain.
The couple got engaged in September when he popped the question with a beautiful vintage Art Deco-style engagement ring – and if reports are to be believed will welcome their first baby together this year.
"I'm very happy," Scarlett told People in January of Romain, a journalist who manages a creative agency. "He's my buddy.
"Being engaged is an exciting time to enjoy and to really savour."
Watch Scarlett talk about Joseph Gordon-Levitt's directorial debut Don Jon...