A concert tour (or simply tour) is a series of concerts by an artist or group of artists in different cities, countries or locations. Often, concert tours are named to differentiate different tours by the same artist and to associate a specific tour with a particular album or product. Especially in the popular music world, such tours can become large-scale enterprises that last for several months or even years, are seen by hundreds of thousands or millions of people, and bring in millions of dollars in ticket revenues. A performer who embarks on a concert tour is called a touring artist. Different segments of longer concert tours are known as "legs". The different legs of a tour are denoted in different ways, dependent on the artist and type of tour, but the most common means of separating legs are dates (especially if there is a long break at some point), countries and/or continents, or different opening acts. In the largest concert tours, it has become more common for different legs to employ separate touring production crews and equipment, local to each geographical region. Concert tours are often administered on the local level by concert promoters or by performing arts presenters. Usually, small concert tours are managed by a road manager whereas large concert tours are managed by a tour manager. Logistics The main challenge in concert tours is how to move the performance's logistics from one venue to another venue, especially for a transcontinental tour. Tour logistics should be very organized and everything has to happen on time and in the right order as planned. Autoweek magazine estimated 30 to 50 trucks were required by Taylor Swift's The 1989 World Tour to bring all the stage, sound equipment, instruments, props, and clothes. When Beyoncé visited the United Kingdom with her 2016 The Formation World Tour, it took seven Boeing 747 air freighters and a fleet of more than 70 trucks to get her stage set and other gear to the venues. The logistics phase of that tour didn't include transportation of the backstage staff, musicians, performers, and the singer herself. Themes The majority of concert tours are part of a promotional campaign to support an album release. Hence, new songs from the respective album are included on its tour's setlist. Some tours are known as "greatest hits tours" or "reunion tour" without any new material or specific album release, such