Running: Rock 'N' Roll Half-Marathon shifted Oct. 31

Expect a lot of costumes on the Benjamin Franklin Parkway on Halloween this year, but of the aerodynamic variety.

That's because the Philadelphia Rock 'n' Roll Half Marathon, which has been run in the city for 38 years, has a new date for 2015, landing on Oct. 31.

Since 1978, the race has been held in Philadelphia on the third Sunday of September. (Until 2009, when bought by Competitor Group, the event was called the Philadelphia Distance Run.) Last year, the event added a 5K on the Saturday before the half-marathon.

The pope's visit, however, the first by a pontiff to the United States since 1979, knocked the race out of its traditional September spot. The pope's Mass on the Benjamin Franklin Parkway on Sept. 27 is expected to bring up to a million visitors to the region. It's connected to the World Meeting of Families, the world's largest gathering of Catholic families, which will be held the week before.

In total, the week is expected to bring up to $417 million in economic impact to the region, and put a strain on the city's resources and available hotels. Adding a 15,000-person race - and shutting down major city arteries on which they would run - was not an option.

Officials from the City of Philadelphia and from Competitor Group worked for months on securing a new date, but this wasn't as easy as moving the race up or back a weekend. The Benjamin Franklin Parkway is used for charity events, charity walks, fund-raisers, and parades throughout the summer and fall. Despite the race's long history, those local, nonprofit events took priority over a race put on by a for-profit company based in San Diego.

"When you factor in all the variables required to host an event of this size and of this nature with road closures, with a start/finish that uses park facilities, and with our need to have an expo at the Convention Center, it came to this was the only weekend that worked," said Alan Culpepper, Rock 'n' Roll's vice president of government relations.

It's being held on a Saturday instead of a Sunday because the National Brain Tumor Society Race for Hope had already been scheduled for Nov. 1. Culpepper said that the events were working together to share resources and reduce costs.

Culpepper said the event won't be curtailed, and may have some added special Halloween-themed elements, though there will not be a 5K this year.

Whether or not it will draw top pros remains to be seen. One reason the race has consistently drawn Olympic and world championship talent is because many pros used the September race as a tune-up for the New York City Marathon. This year, the New York event will be the day after the Philadelphia half-marathon.

Culpepper said that the race could also be popular for American professional runners who would use it as part of their training for the Olympic marathon trials, which will be held Feb. 13, 2016, in Los Angeles. Race officials also expect to draw pros who run shorter distances.

The move is already having a ripple effect on how local runners will compete, too. The Run the Bridge 10K, which draws about 3,500 runners, is traditionally the first Sunday in November - the day after this race. The Philadelphia Marathon and its accompanying half-marathon are scheduled for Nov. 22. Both half-marathons have about the same number of finishers.

Culpepper stressed that the date change is only for this year, and that the event will be moving back to its regular September slot in 2016.