and green channels in order to prioritise customs enforcement. Within the European Union's common customs area, airports may operate additional blue channels for passengers arriving from within that area. For such passengers, border control may focus specifically on prohibited items and other goods that are not covered by the common policy. Luggage tags for checked luggage travelling within the EU are green-edged so they may be identified. In most EU member states, travellers coming from other EU countries within the Schengen Area can use the green lane, although airports outside the Schengen Area or with frequent flights arriving from jurisdictions within Schengen but outside the European Union may use blue channels for convenience and efficiency. A customs area is an area designated for storage of commercial goods that have not cleared border controls. Commercial goods not yet cleared through customs are often stored in a type of customs area known as a bonded warehouse, until processed or re-exported. Ports authorised to handle international cargo generally include recognised bonded warehouses. For the purpose of customs duties, goods within the customs area are treated as being outside the country. This allows easy transshipment to a third country without customs authorities being involved. For this reason, customs areas are usually carefully controlled and fenced to prevent smuggling. However, the area is still territorially part of the country, so the goods within the area are subject to other local laws (for example drug laws and biosecurity regulations), and thus may be searched, impounded or turned back. The term is also sometimes used to define an area (usually composed of several countries) which form a customs union, a customs territory, or to describe the area at airports and ports where travellers are checked through customs. Sanitary and phytosanitary (SPS) measures are customs measures to protect humans, animals, and plants from diseases, pests, or contaminants. The Agreement on the Application of Sanitary and Phytosanitary Measures, concluded at the Uruguay Round of the Multilateral Trade Negotiations, establishes the types of SPS measures each jurisdiction is permitted to impose. Examples of SPS are tolerance limits for residues, restricted use of substances, labelling requirements related to food safety, hygienic requirements and quarantine requirements. In certain countries, sanitary and phytosanitary measures focuses extensively on curtailing and regulating the import of foreign agricultural products in order to protect domestic ecosystems. For example, Australian border controls restrict most (if not all) food