The Dunedin City Council and police will this week have a debriefing to look at how future such events as the unofficial Undie 500 can be handled.
The police clashed with crowds in Dunedin on Saturday night, with officers in riot gear cracking down on a bottle-throwing mob.
The trouble began just after midnight when emergency services were called to a fire in Castle Street. Students had been involved in the unofficial Undie 500 rally.
Inspector Lane Todd says there were 30 arrests for a range of offences, from disorderly behaviour to breaching the temporary alcohol ban.
He says about 40 additional team policing officers were called because of the 300-strong crowd.
Dunedin's mayor Peter Chin has described the clash as disappointing.
Otago University Students' Association president Simon Wilson says a bottleneck was created when people flooded out of Gardens Tavern on Castle Street, a prominent student pub.
He says after a small group decided to block the path of police, officers in riot gear responded with "justified" force.
Mr Wilson says with 30 arrests, only 12 of which he claims are Otago University students, this year's trouble was fairly minor compared with last year.
Radio New Zealand's reporter says bottles and rocks were thrown at the police, as they formed skirmish lines to force the group off the streets and into the Otago University campus.
Gradually, the group got smaller, and dispersed completely after about an hour and a half.
About 100 officers patrolled north Dunedin streets on Saturday, and at about 10pm they were confident there wouldn't be any trouble.
Mr Wilson says the hype and mythology surrounding the event causes problems.
"We've seen over the last couple couple of years people expecting things to happen," he says.
"There was a large number of non-students who you wouldn't normally see down there on a Saturday night, turning up, almost looking for trouble or looking to see trouble."
The authorised Undie 500 was cancelled this year, after last year's event ended in riots and 70 arrests.
Polytechnic Students' Association co-president Ryan Ward says mass disorder at last year's Undie 500 damaged the reputation of all Dunedin students.
The association is threatening to expel any of its members found guilty of illegal activities during any Undie 500 related events.
