DULUTH – All eyes in the international running community are looking at Grandma's Marathon, which is poised to be one of the largest in-person races held since the COVID-19 outbreak.

Organizers of the Duluth event, scheduled for June 17-19, have teamed up with world experts on crowd control to devise a plan to safely host 9,500 runners signed up to compete in the marathon, half-marathon and 5K races.

"We're all basically looking at Duluth," said Marcel Altenburg, a crowd scientist at the U.K.'s Manchester Metropolitan University who has studied the flow of the world's largest marathons in places like London, Berlin, Chicago and New York.

The OUC Orlando Half Marathon hosted 1,700 runners in December, but planners of Grandma's Marathon believe it will be the first race of its size since the pandemic's onset.

Altenburg is using crowd science software developed around the world's biggest races to help Grandma's organizers ensure that participants and volunteers can stay socially distant. He uses technology like Google Earth and Google Maps to model the course and then inputs past results to simulate the event.

Altenburg found that if Grandma's staggers its starting line properly, each runner should be able to have at least 12 feet of separation from others at any given moment.

"All in all, it was 9.6 million calculations in order to literally check every single overtaking that happens on the course," he said.

Greg Haapala, Grandma's Marathon race director, said there are still lots of uncertainties surrounding the June event. He and others are in the midst of conversations with the state about changing public health guidelines so that races can have more than 250 people on a course at once.

"We're sort of trying to work on this math problem together so that we can bring the data to the state to help show that we think this can be done in a safe manner if all the elements are right," Haapala said.

Organizers said runners will be bused in groups of 25 to the starting line, where they will be released in waves of five. Anyone who is not actively running the race must wear a mask, and spectators will likely not be allowed.

Registrations for Grandma's 2021 races filled up in December, after organizers announced the event would be capped at half capacity. Last year's race was canceled for the first time in its 44-year history.

"We really focus on the mission of our organization, which is getting people active and keeping people healthy," Haapala said. "Events often are the motivational factor that keep people [going] after their goal."

The Duluth event is the 12th largest marathon in the country and one of the few races in the summer. Many of the most popular spring contests — like the Boston Marathon and the London Marathon — have postponed their 2021 races to the fall.

"That's part of the reason we're in this position," Haapala said. "Being in Duluth, so far north and right on the lake, we're one of the few places that can still have really good running weather into June."

Twin Cities in Motion is also consulting with Altenburg about the upcoming Medtronic Twin Cities Marathon scheduled for October. Virginia Brophy Achman, executive director of the marathon's nonprofit organizer, said the event would likely have a reduced capacity, though more details will be announced in early spring.

"Everyone is preparing for this one race to make a start for the season and hopefully break the ice," said Altenburg, who has received calls from race organizers in London and Australia asking about plans for Grandma's Marathon. "They have all the ingredients to work."

It helps, for instance, that the course is less urban than many major marathons, and it's a point-to-point race instead of a loop.

"If it's the right time," he added, "it's this race that will make the big comeback hopefully for the whole U.S."

Katie Galioto • 612-673-4478