It was the largest demonstration in the Serbian capital for weeks, and despite the stench of exhaust from the rickety Yugo cars, the mood was irrepressibly optimistic as opposition leaders once again demanded that their victories in November's municipal elections be recognised.
The police, sitting in a collection of rusty coaches and patrol cars parked outside the parliament building, kept their own engines running but were unable to do more than look on bemused.
Just before Christmas, the government banned marches on non-pedestrian streets, restricting the demonstrators to a small cluster of cobbled shopping alleys and raising the tension between them and riot police lined up a few yards away. Yesterday's car blockade broke that deadlock, further raising the pressure on President Slobodan Milosevic as he seeks a face-saving way out of the crisis.
The opposition, fearing the possibility of a violent crackdown, made a special effort not to antagonise the police, saying they sympathised with the fact that they had to waste their time on the streets and urging them to join the protests. The crowd waved at the police van and brandished sprigs of foliage, a symbol of peace for the Serbian orthodox Christmas which falls tomorrow.
Mr Milosevic was under further pressure from Nebojsa Covic, the outgoing Mayor of Belgrade and a moderate member of Mr Milosevic's Socialist Party, who threatened to resign this weekend amid clear signs of disagreement with his leader. Mr Covic is known to be strongly opposed to police intervention in the crisis, and yesterday an opposition newspaper reported that he had met Mr Milosevic and urged him to recognise the election results in full.
The students, who have been demonstrating alongside the opposition in Belgrade, made their own ultimatums, meanwhile, saying they would start a permanent round-the-clock protest on the streets from Thursday unless the riot police were removed before then.
They have organised meetings for this morning with the interior minister, who is responsible for the police, and the armed forces chief of staff.