In today&#8217;s fragmented media environment, &#8216;engagement&#8217; seems to be the &#8216;in&#8217; metric by which all advertising effectiveness is measured. It&#8217;s no longer sufficient to build awareness and brand preference &#8211; increasingly, it&#8217;s about creating sticky relationships with consumers, and getting them to interact and transact with your brand wherever they may be. Today&#8217;s advertising is about talking with consumers, not at them, building mutually beneficial relationships, and turning consumers from customers into brand advocates.&#160;So how can advertisers create these enhanced two-way relationships? By using one of the oldest media in existence, media that dates back to circus posters and horse-drawn streetcar advertising in the mid-1800&#8217;s: Out of home advertising.Why out of home? Because while digital, social and mobile advertising platforms have been dominating the discussion and grabbing a huge share of the media pie, the out of home advertising industry has been quietly and systematically rethinking its role in the media mix and innovating like crazy to drive increased consumer engagement.This may feel counter-intuitive to some. If you haven&#8217;t taken a look at out of home lately, you probably think it&#8217;s all about highway billboards, the occasional bus wrap, or a Times Square spectacular. But the reality is quite different. Out of home advertising is undergoing a dramatic transformation, and is now the second fastest growing advertising medium in the United States, increasing at about 5% a year and outpacing all other media except online.Over the past few years, the out of home industry has embraced innovation and technology, collectively investing hundreds of millions of dollars to upgrade its digital and interactive capabilities to take advantage of the convergence of online, social and mobile media.Quite simply, out of home advertising is now a highly effective, highly engaging advertising platform, accelerating and amplifying online, social and mobile advertising campaigns by allowing consumers to interact and transact with brands through their mobile devices &#8211; anytime, anywhere, during the 70% of their waking hours when consumers are away from home.One of out of home advertising&#8217;s greatest strengths has always been its ubiquity, reaching consumers where other media don&#8217;t go, wherever and whenever they commute, work, shop, travel and play while away from home. When you layer on top of this digital billboards, interactive touch screens, Near Field Communications, and a host of other advanced technologies like geotargeting and augmented reality, advertisers now have the ability to interact, engage, and transact like never before, to create genuine, two-way brand relationships.Digital conversion of billboards, posters, bus shelters, street furniture and other place-based advertising formats has revolutionized the role out of home advertising plays in the media mix. Out of home displays now feature interactive web URL&#8217;s and live Twitter feeds. They offer free music, book downloads and coupons. They catch criminals and serve the community with real-time FBI Most Wanted lists, Amber Alerts and FEMA warnings. They geo-target by neighborhood. They are day-parted at the click of a mouse to tout coffee in the morning and French fries at night. They even act as virtual supermarkets, so that time-strapped commuters can order eggs and milk with their mobile devices while waiting for a train in the morning and have them delivered when they arrive home at night. When you consider that only a small percentage of out of home&#8217;s total inventory has been converted to digital so far, you begin to see that the sky is truly the limit for out of home advertisers.More and more, out of home advertising is a vital and strategic component of brand launch media plans. On October 15th, Paul McCartney launched his upcoming album &#8220;New&#8221; on digital billboards and screens in 18 countries simultaneously around the globe. The campaign featured sight, sound and motion, and encouraged consumer engagement with free mobile samples and music downloads. According to William Eccleshare, CEO of Clear Channel Outdoor, &#8220;Out of home combined with mobile is the next great advertising platform. Campaigns like these drive people to their mobile devices, and we can now demonstrate that they drive consumer engagement.&#8221;Out of home&#8217;s biggest advertisers like McDonald&#8217;s, Verizon, Samsung and Apple have already recognized the power and potential of out of home engagement. But admittedly, we have a bit of an image problem with some advertisers. The industry is doing everything it can to change the perception that out of home is &#8216;signs on sticks.&#8217; Globally, out of home is a $30 billion market. Its share of total advertising spend is 8% in England, 11% in France and 16% in Hong Kong. It is only 4.9% in the United States.So, out of home clearly has some catching up to do. But, continuing to tell this incredible (and to some, surprising) story of innovation should go a long way in getting advertisers to think differently about out of home advertising.Nancy Fletcher was elected President &amp; CEO of the Outdoor Advertising Association of America (OAAA) in 1992 and is responsible for advancing the legislative, marketing, and product improvement goals for the out of home (OOH) advertising industry in the US.Fletcher is an attorney and industry authority, with 35 years of experience in OOH advertising. Before joining OAAA, Fletcher served as an officer for Patrick Media Group, the largest OOH media company in the US at that time. She concurrently was elected Chair of the Board of Directors for OAAA.&#160;Currently, Fletcher serves on the Board of Directors of OAAA, the Ad Council, the Traffic Audit Bureau, and Teach for America. She is the former Board chair for National Cathedral School and President of the Fletcher Family Foundation.Check us out on Facebook at MediaBizBloggers.comFollow our Twitter updates @MediaBizBloggerThe opinions and points of view expressed in this commentary are exclusively the views of the author and do not necessarily represent the views of MediaBizBloggers.com management or associated bloggers. MediaBizBloggers is an open thought leadership platform and readers may share their comments and opinions in response to all commentaries.