motorists traveling in both directions. The center lane is narrower than two vehicular travel lanes and has no centerline; some are narrower than the width of a car. Cyclists are given preference in the bike lanes but motorists can encroach into the bike lanes in order to pass other motor vehicles after yielding to cyclists. Advisory bike lanes are normally installed on low volume streets. Advisory bike lanes have a number of names. The U.S. Federal Highway Administration calls them "Advisory Shoulders". In New Zealand, they are called 2-minus-1 roads. They are called Schutzstreifen (Germany), Suggestiestrook (Netherlands), and Suggestion Lanes (a literal English translation of Suggestiestrook). Bicycle highways Denmark and the Netherlands have pioneered the concept of "bicycle superhighways". The first Dutch route opened in 2004 between Breda and Etten-Leur; many others have been added since then. In 2017 several bicycle superhighways were opened in the Arnhem-Nijmegen region, with the RijnWaalpad as the best example of this new type of cycling infrastructure. The first Danish route, C99, opened in 2012 between the Vesterbro rail station in Copenhagen and Albertslund, a western suburb. The route cost 13.4 million DKK and is 17.5 km long, built with few stops and new paths away from traffic. "Service stations" with air pumps are located at regular intervals, and where the route must cross streets, handholds and running boards are provided so cyclists can wait without having to put their feet on the ground. Similar projects have since been built in Germany among other countries. The cost of building a bicycle super highway depends on many things, but is usually between €300000/km (for a wide dedicated cycle track) and €800000/km (when complex civil engineering structures are needed). Cycling-friendly streetscape modifications There are various measures cities and regions often take on the roadway to make it more cycling friendly and safer. Aspects of infrastructure may be viewed as either cyclist-hostile or as cyclist-friendly. However, scientific research indicates that different groups of cyclists show varying preferences of which aspects of cycling infrastructure are most relevant when choosing a specific cycling route over another. Measures to encourage cycling include traffic calming; traffic reduction; junction treatment; traffic control systems to recognize cyclists and give them priority; exempt cyclists from banned turns and access restrictions; implement contra-flow cycle lanes on one-way streets; implement on-street parking restrictions; provide advanced stop lines/bypasses for cyclists at traffic signals; marking wide curb/kerb lanes; and