One of the world's toughest races, the Badwater 135 Ultramarathon, returns to its namesake location next year in Death Valley National Park after federal park officials barred it in 2014 over safety concerns.

The race is named for Badwater Basin which, at 282 feet below sea level, is the lowest point in the Continental United States. It's also famous for recording the hottest temperature on earth. So of course, that's where adventure-seeking ultrarunners go in mid-July to test themselves in temperatures that can exceed 120 degrees.

The biggest change in the new rulebook requires the race to begin after sunset under a full moon. That shift in starting times will give most runners about 50 miles of cooler overnight temperatures as they run through the moonlit Death Valley National Park.

"It's still going to be hot," said race director Chris Kostman. "Even in the middle of the night it's 90 degrees in Death Valley in the summertime."

The race was first run in 1977 and has been held annually since 1987. Through 1995, the race began after sundown, so reverting to the later start isn't such a break with tradition, Kostman said.

In recent years the 100 athletes allowed into the invitational race would start in waves during the day, so most of their run through Death Valley was in full blazing sunlight on asphalt whose radiant heat could melt shoes and blister feet.

The race goes over two mountains and ends at Mt. Whitney Portal, near the highest point in the Continental U.S. Runners climb about 13,000 feet over the 135 mile race, finishing in about 24 to 48 hours.

In October 2013, Death Valley National Park officials withheld permits for the 2014 edition of Badwater and other endurance races until they wrote new safety rules.

The Park Service wanted the new rules out of concern for the safety of runners and Park Service workers. Its report on the new rules said the park seemed to be giving visitors a mixed message by telling tourists not to exert themselves during the highest summer temperatures, yet permitting the Badwater 135 Ultramarathon to take place.

Kostman said that Badwater runners are among the best-trained for the hot and rugged conditions and that no runners have died or been seriously injured in the race.

The National Park Service had little data on injuries during endurance events, it said in its safety recommendations document. It said race organizers were not reporting injuries and accidents to park officials as the permits required, even though photos from various events (Badwater and others) made it clear that injuries had occurred.

The new rules do not permit extreme sporting events in temperatures over 110 degrees, or at night unless there is a full moon to make the terrain more visible, said Cheryl Chipman, a National Park Service spokeswoman.

Other concerns were for the athletes' support crews and vehicles negotiating around each other, the runners and Death Valley tourists on the two-lane roads that had blind curves and sudden drop-offs. The new rules cut the number of support crew members to four from six and allow just a single support vehicle per runner rather than two, Chipman said.

"We're happy to host the event again, and hope it will be safe for everyone," Chipman said.

Cincinnati ultramarathoner Harvey Lewis won last July's race in just under 24 hours on an alternate course outside the park that was cooler but included more mountain running. He wants to defend his title on the traditional Death Valley course, which he has run three times before.

"It represents the most challenging elements that the human body has the opportunity to endure," Lewis said. "I was quite happy to see it return to its rightful home."

The race is set for July 28.