NEW YORK -- Travelocity and Expedia are the most valuable brands in online travel, and their brand equity plays a key role in driving traffic to their sites, according to a new study released by ACNielsen International Research, a business unit of VNU.

The study, the first of its kind to examine the brand equity of U.S.-based online travel providers, found a strong correlation between brand equity and the number of unique visitors to a travel web site.

Based on Internet audience data compiled by Nielsen/NetRatings (a sister VNU business), Expedia and Travelocity ranked number one and number two as the most-visited travel Websites during the study period.

"Strong brand messages that resonate with consumers are very important to the online travel industry, and can make a big difference in the success of a travel Website," said Deepak Varma, senior vice president at ACNielsen International Research. "Online travel marketers need to better understand their brand equity so that they can either strengthen their already strong brand positions, like Travelocity and Expedia, or take actions to boost brand equity and drive more traffic to their sites."

Not surprisingly, the ACNielsen study found that consumer awareness was the foremost factor driving brand equity. ACNielsen defines "brand equity" as the distinct effect brand knowledge has on consumer response to marketing activity -- the relationship between what a consumer knows about a brand and what a consumer does as a result of this knowledge.

By understanding a brand's equity in the minds of consumers, marketers can develop more effective marketing plans, enhance product offerings, and hone pricing strategies.

After reviewing more than 80 travel sites, ACNielsen found that drivers of brand equity in online travel clearly differ by travel category.

"Travelocity and Expedia have become household names in online travel through very effective advertising," said ACNielsen's Varma. "However, when booking air travel or making hotel reservations, consumers have very specific needs and expectations, which often differ from category to category. This is where online travel category specialists such as Hotels.com can compete effectively with the generalist sites and build brand equity with consumers."

Along with driving brand equity for travel sites overall, consumer awareness is also the most important factor in determining brand equity for each of the five online travel categories studied -- air, hotels, car rentals, vacation packages and cruises.

However, when comparing the key drivers of brand equity across categories, the relative importance of other attributes becomes apparent.

"The brand marketing strategy for each online travel provider should be unique for each of the categories in which it competes, and tailored to the importance consumers place on differing brand aspects," noted Varma. "For instance, Southwest Airlines' Website provides the customer with simplicity and ease of navigation, a unique point of distinction from other airline travel sites and one that resonates well with online air travelers."