LOS ANGELES (AP) — “The Amazing Race” host Phil Keoghan is glad he’ll never be asked this question ever again: Why isn’t the race broadcast in high definition?

After years of sticking to standard definition, CBS’ around-the-world competition expands to HD for the first time Sunday with an “Unfinished Business” edition starring former contestants.

“For a long time, people have said to me that they couldn’t believe we weren’t in HD,” said Keoghan. “For me, it was just very frustrating because I didn’t disagree with them. I think if there’s any show on prime-time network television that lends itself to HD, it’s ‘The Amazing Race.’ It screams for HD, and it’s been screaming for HD for a long time.”

Several other reality TV shows have been broadcast in HD for years. (CBS’ “Survivor” upgraded to HD in 2009.) After years of blaming the expense and challenge of using HD equipment on the road, “Amazing Race” producers made the change for the 18th season, promising crisp images of racers climbing a glacier in Switzerland and interacting with animals in China.

The switcheroo is striking in the premiere episode when 11 teams of veteran contestants who have never won the show’s $1 million grand prize set off from a wind farm in Palm Springs, Calif., for sunny Sydney, Australia, where the challenges include diving into a murky shark tank and navigating a 16-foot skiff along the glistening Manly Cove.

“Visually, it will be a much richer show,” promised executive producer Bertram van Munster. “We’re glad that CBS gave us the greenlight to do this in HD. We didn’t do so bad in the regular format. We won the Emmy for best reality television cinematography, but now we can go a little further with our new modern technology on those big beautiful flatscreens.”

The move to HD didn’t dictate this season’s course, said van Munster, which includes stops in Yokohama, Japan; Lijiang and Kunming, China; Kolkata and Varanasi, India; Vienna, Austria; Zermatt, Switzerland; and Rio de Janeiro, Brazil. For the first time, the race will visit Liechtenstein, where teams were tasked with measuring the landlocked country on mo-peds.

“I think one of the great aspects of this race is all the stark contrasts,” said Keoghan. “For example, going from Varanasi to Zermatt, you’ve got this hot, colorful place in Asia then a very cold, snowy place in Europe. The teams that were racing through those countries were able to see the extreme differences, and we’re able to show that off in HD.”

Several game-changing twists return for the “Unfinished Business” edition. In the premiere, Keoghan informs the players that the last team to arrive on the mat will automatically face a U-turn, forcing the duo to perform both Detour challenges, while first-place finishers will receive the Express Pass, allowing a team to skip one task during the race.

On the first leg, alliances form when friends Justin Kanew and Zev Glassenberg give up a clue to struggling Nathaniel “Big Easy” Lofton and Herbert “Flight Time” Lang, the Harlem Globetrotters who competed with them on the 15th season, but Kanew dismisses 14th season vets Margie and Luke Adams, and Jaime Edmondson and Cara Rosenthal when they ask for help.

“We’re very aware that five of these teams know each other from competing on the same season,” said Kanew during an interview before the race began last November. “Zev and I have definitely talked about it. There might be a natural alliance with them, especially in the beginning before we get to know them. Luckily, none of those teams scare us.”

Other racers from the 14th edition include sisters LaKisha and Jen Hoffman, engaged couple Amanda Blackledge and Kris Klicka, and father and son Mel and Mike White. Dating couple Kent Kaliber and Vyxsin Fiala and father and daughter Ron and Christina Hsu hail from the 12th season, while cowboy brothers Jet and Cord McCoy are the only team from the 16th season.

Gary and Mallory Erwin skipped their season finale party in New York to be able to run “The Amazing Race” back to back. The father and daughter duo from the 17th installment only had a few months of downtime before heading back around the globe. Mallory joked before the race began last year that she and her father “still had our bags packed.”

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