Hillary Clinton hits the campaign trail in a van named Scooby

As a private citizen, Hillary Clinton flew on private jets to lucrative speaking engagements. As a Democratic presidential candidate, she is travelling her first 1,600km in a van nicknamed "Scooby".

Clinton's decision to drive, rather than fly, 16 hours to her first campaign appearance in Iowa set off a scramble by national media outlets to track her down one day after she announced her second bid for the presidency through an online video.

CNN reported she was spotted at a petrol station in Pennsylvania on Sunday. On Monday, a local TV station in Toledo, Ohio, reported that she ordered the chicken bowl with guacamole at a nearby restaurant from the Mexican chain Chipotle.

Outside Chicago, media trucks staked out a quiet residential block in suburban Park Ridge with hopes that Clinton might stop by her childhood home.

It was the latest game of cat and mouse for a public figure who has had a prickly relationship with the news media since she first became a national figure as the wife of then-Arkansas Governor Bill Clinton, who was elected president in 1992.

Clinton's aides are seeking a low-key campaign to avoid the perception of entitlement that hampered her failed 2008 bid. Her first events scheduled for yesterday and today in Iowa, the state where the 2016 presidential nominating contests begin, will be roundtable meetings with small groups of voters.

Aides said the trip was Clinton's idea, and that they were not sure they were going to make it public until CNN received a tip from someone who spotted her in Pennsylvania.