Four years ago, on the Monday after Lollapalooza 2008, the tornado sirens went off in the city of Chicago for the first time in the 20 years I’ve lived here. Raised on the east coast, I was startled when my wife grabbed me by the hand to cower in the basement for 45 minutes until the all-clear. What would have happened, I wondered, if the warning tolled 24 hours earlier when 150,000 people were in Grant Park? (This year, the city has approved attendance of 300,000.)

I wrote a piece for the Sun-Times trying to answer that question, but I had little luck getting an answer as city spokeswomen stonewalled me. The people in the northern end of the park, it seemed obvious, would be directed to the underground parking ramps below Millennium Park. But what of the 75,000 (now 150,000) filling Hutchinson Field, in front of Lollapalooza’s main stage, and the rest of the southern end of the park?

Soldier Field, which would be locked, is a long hike across Lake Shore Drive, and the hotel basements on Michigan Avenue, which never could accommodate that size crowd, are no closer. In severe weather, the park would need to be cleared on short notice, without panic, and with clear directions on where people should go. Shouldn’t the plan be publicized in advance?

At the time, police spokeswoman Monique Bond and Office of Emergency Management & Communications spokeswoman Jennifer Martinez both assured me that the city had an evacuation plan—though neither would tell me what it was, because of “terrorist concerns,” they claimed.

In a hard-hitting story in today’s Chicago Tribune written by Heather Gillers — the paper’s new investigative entertainment reporter who won nationwide acclaim in her last gig for her coverage of the Indiana State Fair stage collapse — the question of the specifics of the Grant Park evacuation plan still remains unanswered, as does another that had not occurred to me: Who will cancel or suspend the show and take control of an emergency evacuation if one is needed? Writes Gillers:

The written plan is unclear on what would happen if the safety officials and the promoter are in conflict — a situation that can stifle quick decisions. That type of conflict likely contributed to tragedy in the weather-related collapse of a stage structure last year in Indianapolis.

An independent expert who analyzed what happened at the Indiana State Fair, where seven concert-goers were killed, said plans should leave no ambiguity about who makes the final call in an emergency.

“It is not in the best interest of public safety to have ambiguity about who is responsible for the decision about whether the show should be delayed,” said Charlie Fisher of Witt Associates, which conducted an eight-month independent assessment of emergency preparedness by the Indiana State Fair.

“It should be very clear: ‘This is who is going to make the call,’ and ‘This is how the call is going to be made.’”…

Carol Cwiak, assistant professor of emergency management at North Dakota State University, said sometimes cities agree to emergency-weather plans that enlist promoters in decision-making because it makes the city a more attractive place to hold an event.

“It will limit private-sector partners from wanting to come into those jurisdictions and do events if they feel like their control is removed,” she said.

But she said cities should be careful when sharing that authority.

“The promoter has a monetary interest,” Cwiak said. “They probably want to take care of people as well. But that’s not their primary interest.”

[Lollapalooza spokeswoman Shelby] Meade said: “[Lollapalooza promoter] C3 has no financial incentive to, nor interest in, proceeding with a festival that would endanger fans.”

Can we really accept that, however, when for the last eight years, Lollapalooza has skimped on security and fencing, allowing large crowds of gate-crashers to rush the event — endangering fans and themselves? The promoters have promised much tighter control of that issue this weekend. But, as with the weather, they have to date simply been lucky that serious injuries have been minimal, many concert professionals and industry watchdogs have said.