most essential piece of equipment for a bicycle messenger is a bicycle. Some large cities that employ significant numbers of bike messengers (e.g., New York City) have relatively flat terrain, and are especially conducive to the performance properties of fixed-gear bicycles. Because bicycle thefts are prevalent in many cities, a lock to secure the bike during deliveries is essential. U-locks are also popular. Messengers typically carry basic tools, weather-proof clothing and a street map. It is also common for messengers to carry storage clipboards for manifests, receipts, and/or other logistic documents. The majority of messengers use a bag to carry deliveries and personal effects. Bags with a single strap that wraps diagonally across the chest (popularly known as messenger bag) are popular because they can be swung around the messenger's body to allow access without removing the bag. Clasps which can be adjusted with one hand (ideal for riding), clips, pockets, and webbing loops on the strap for holding a cell phone or two-way radio and other equipment also feature on purpose-built messenger bags. Bags generally have large capacities (up to 50 liters or 3,000 cubic inches). Baskets and racks mounted on the bike are also used, and at least one messenger service (in New York City) equips its riders with specialized three-wheel cycles (sometimes known as cargo-trikes), with a large trunk in the rear. Besides cargo-trikes, many messengers choose to ride various forms of cargo bikes for delivering large objects or high volumes of deliveries. Many bicycle messengers also wear helmets and mount lights and fenders (mudguards) to their bicycles. Communications Messengers communicate and are dispatched to assignments via hand-held communication devices including two-way radios, cell phones, and personal digital assistants. Many of the larger messenger services equip their riders with GPS tracking devices, for ease of location. Messenger culture and influence Media Messengers have been used in fiction media as symbols of urban living, and have been the subject of novels, memoirs, feature films, television series, comic-books, and sociological studies. Mexican artist José Guadalupe Posada created a popular icon of a marijuana-smoking bicycle courier everyman in his 19th-century engravings. The 1986 film Quicksilver featuring a bicycle messenger, is an early expression of the mythology of the messenger as a daredevil stunt rider. Star Kevin Bacon rides a racing bike, a fixed gear bike and a trick bike with 1:1 gear ratio and zero-rake forks, to perform the stunts