The expanded functionality for the popular travel app comes just as the summer travel season kicks off. Hotels.com is seeking to drive traffic to the app and to its Web site with a suggested itinerary of three ?road trips? for summer travelers. 

?We have added some new features to the app that make it easier for trip planning,? said Taylor L. Cole, a Dallas-based spokeswoman for Hotels.com. 

Other new features include a mobile-app version of the ?deals of the day? feature that has been popular on the desktop version of the Web site. The app also uses a location finder to offer ?deals for tonight? in the vicinity of the user. 

London-based Hotels.com also carefully tracked how its mobile app users were navigating the app, and also how they were using the desktop version of the site. Customers were interested in both reading and posting reviews, for example. In the app, there are now two tabs that allow users to toggle back and forth between reviews posted on TripAdvisor and those posted on Hotels.com. 

?Our experience with how customers use us on mobile helped inform our decisions,? Ms. Cole said of the app upgrades. 

The partnership with TripAdvisor is one example of how Hotels.com has expanded the content available on its mobile app. The company also revamped the site to provide improved photo viewing for mobile tablets, and it made more content about each hotel available to app users. 

Stephen Kremser, a partner at Boston Consulting Group and co-author of a recent report on mobile travel, said travel apps are improving their functionality and appearance at a rapid pace. 

?The gap between what you are seeing on the desktop and what you are seeing on the mobile app is closing fast,? he said. ?There is a broad trend around improving functionality on mobile travel apps.? 

Mr. Kremser also said that offering the ability to read reviews is a feature that is growing in popularity for mobile travel apps. He cited Southwest Airlines and Carnival Cruise Lines as two travel companies that have added reviews to their mobile apps. 

?At the end of the day, you are trying to prevent the consumer from going somewhere else to get that content,? Mr. Kremser said. 

In the Hotels.com ?Top Summer Road Trip Itineraries? promotion that is encouraging the use of its app, Hotels.com suggests three road trips ranging in distance from about 650 to 1,1,00 miles. The trips are a ?Live Music Road Trip? through the Southeast; a ?Ballpark Tour? through the Northeast; and a ?Southern BBQ Tour? through the South. 

The Hotels.com app has had more than 25 million downloads, Ms. Cole said. 

Hotels.com attracts relatively high interest among its total base of online users. In February, it had 1.1 million unique visitors via mobile, or about 25% of its desktop visitors, according to the report from Boston Consulting Group. That percentage of mobile visits outpaced both Expedia and Priceline. 

?We continue to grow, and we are gaining traction in both iOS and Google Play,? Ms. Cole said.