The Papal Visit : Estimating Crowd Size Takes Math, Copter--and Almost a Miracle

With news media clamoring early Tuesday for an official estimate of the crowd along the papal motorcade route, the Los Angeles Police Department’s chief spokesman responded with a guess.

Based on sketchy reports from officers who did a quick “fly-by” in a helicopter, reports from other officers on the ground, and looks out a police headquarters window and at televised coverage of the motorcade, Cmdr. William Booth estimated that 500,000 to 700,000 people were lining the seven-mile route.

Booth later revised his figure dramatically downward to a maximum of 300,000.

The city Department of Transportation put the number possibly as low as 150,000 and as high as 250,000.

The disagreements demonstrated that counting large crowds is an inexact art, frequently influenced by the politics of the practitioner.

As Booth acknowledged after the revision, “If we were going to err, we figured we’d err on the side of the Pope.”

Colored by Anticipation

Booth said he had been influenced by “our anticipation” of a much larger crowd.

The Los Angeles archdiocese had forecast a crowd of between one and two million.

The truth is “no one knows” how many people lined the route, said Police Lt. Dan Cooke, a Booth colleague who is frequently called upon to estimate crowds.

Cooke’s favorite method is to count the number of people who are standing between a set of lampposts or telephone poles and then multiply them by the number of the lampposts or telephone poles en route.

He did that on a section of Main Street on Tuesday and that contributed to the downward revision.

“I suspect that Einstein would have blessed (Cooke’s) method,” Booth said.

Calculation Method

If Cooke is estimating the number of people in a defined area, he takes the number of square feet, and halves it if the crowd is dense.

Two square feet is about the amount of space a person has in a crowded elevator, said Don Howery, general manager of the city’s Department of Transportation, which did its own estimates.

“There are books on it,” Howery said.

Engineers in Howery’s department did their own estimates.

In advance of the pontiff’s arrival, they measured sidewalk space along his route and calculated that the sidewalks could hold a maximum of 400,000 people.

Their calculations were complicated.

Certain Blocks Measured

Thomas Conner, a city traffic engineer, explained that selected blocks along the route were measured and found to vary from about 400 to 600 feet long. Sidewalks were found to vary from 10 to 15 feet wide.

Space on selected blocks was calculated. Then planners extrapolated to estimate space on the whole route.

For example, in the case of a 600-foot-long block with a sidewalk 10 feet wide, planners multiplied width times length for a total of 6,000 square feet in which people could stand.

Then they subtracted about 15%--or 900 square feet--for intersection space that people could not stand in and space occupied by lampposts, telephone poles and the like.

Then they divided by two square feet per person--”crush conditions,” Conner said--to find that 2,550 spectators could stand on that block.

Put another way, they calculated that there would be room for people to stand about eight deep.

Not That Deep?

But after the parade ended, airborne observers, including Howery and some police officers, decided that people had lined the route at an average of about three deep.

“What I guess we’re saying,” Conner said, “is that 150,000 of the (possible) 400,000 (sidewalk spaces) were filled.”

Of course, not all intersections were closed, so additional people could have stood in them. And an unknown number of others undoubtedly watched from buildings along the route.

“When we sat down after the parade was over, with the police in the command center, and conferred with people in helicopters who had observed the entire route . . . the consensus was that 150,000 to 200,000” people had watched the parade from sidewalks and streets, Conner said.

But flexibility was the order of the day.

Howery said late in the day that the crowd ranged from 150,000 to 250,000. But when he was told that the official police estimate was still 300,000, he was agreeable. “I’d say it could have gone as high as 300,000,” he said.