When Contiki Holidays first started working with YouTubers, about 25% of the travel company’s marketing budget was digital.

Now, three years later, that portion is approaching 65% — and like any great adventure, there’s no turning back.

“Hashtag .. NoRegrets,” jokes Contiki Canada’s president, Brad Ford, referencing the company’s global video campaign, stated in Canada in which YouTubers vlog about their experiences while on a Contiki holiday. “It just became clear to us that in terms of overall reach, the digital spend was so important,” he says.

The latest reincarnation of the influencer-focused marketing campaign is a European road trip in the Contiki coach, driving along the Mediterranean with 13 YouTubers on board. Participants include some of YouTube’s biggest stars including Joey Graceffa, Smosh’s Anthony Padilla and his finacée Kalel Cullen.

Along the journey, which kicks off Thursday, the vloggers will produce unscripted content for their own channels as well as contiki.com/roadtrip. As per usual arrangement with the youth-focused adventure-tour company, the talent is not paid for their videos or to promote the brand. However, they do get a free trip, a lot of inspiration for their channels, and the chance to engage subscribers and give away prizes through a series of challenges. Contiki is also organizing a fan meet-up in London towards the end of the trip.

This year’s group of road-tripping content creators has a combined 13 million subscribers: among them are Jesse and Jeana (BF vs. GF), Alli Speed, Lilly Singh (IISuperwomanII), Shannon Harris (Shaaanxo), and Justin James Hughes.

Contiki’s digital media strategy has proven to be an effective way to reach young travelers.

“What has really moved the needle for us is 15-second and 30-second pre-roll that we see through various channels, directing back to the full video that we associate with the campaign,” says Ford, about measuring success and customer acquisition rates. Through promo codes, they’re able to track how many people book trips after viewing the videos. Last year, for example, Contiki determined that 35% of all their 2013 sales occurred within the 8 weeks the #NoRegrets adventure challenge ran.

Another reason the brand works with vloggers is because they are natural raconteurs with the ability to develop fun, factual travel diaries that connect to Contiki’s core values.

“It’s about reconnecting to the storytellers — the people who are legends in our eyes, who have some some incredible things to say,” says Ford.

“Legends” is actually the name of Contiki’s upcoming second phase of the campaign, which is about collecting the best stories from Contiki adventures, with the chance for one of them to be given the “Hollywood treatment.” That includes having a celebrity bring that story to life in a feature, Ford says. The Legends campaign will run through 2015, with more details to be announced at a later date.

This summer’s Contiki YouTuber RoadTrip, which has stops in Barcelona, Nice, Florence and Rome, runs from Thursday to Aug. 4.