It was intended to make the expressways free when they are paid off. The Meishin Expressway and Tomei Expressway debt has been fully paid off since 1990. It was decided in 1972 that tolls would be pooled from all expressways to provide a single source of operating funds, since some sections were little used. Earthquake resistant construction methods have added to costs, as well as extensive soundwalling. In March 2009 (then) Prime Minister Taro Aso unveiled a plan to reduce tolls to ¥1,000 on weekends and national holidays. Tolls on weekdays would be cut by around 30 percent. According to the National Expressway Construction Association, 4.41 million vehicles use the expressways daily, driving an average of . National expressways make up the majority of expressways in Japan. This network boasts an uninterrupted link between Aomori Prefecture at the northern part of Honshu and Kagoshima Prefecture at the southern part of Kyushu, linking Shikoku as well. Additional expressways serve travellers in Hokkaido and on Okinawa Island, although those are not connected to the Honshu-Kyushu-Shikoku grid. Features Most expressways are four lanes with a central reservation (median). Some expressways in close proximity to major urban areas are six lanes, while in rural areas are constructed as undivided two-lane expressway. Two-lane expressway sections are built to a standard that allows conversion to four lanes in the future. Speed limits for passenger cars, motorcycles, and buses defaults to with a minimum speed of , unless otherwise posted. The maximum speed limits for heavy trucks, trailers and three-wheelers are set at . Vehicles unable to reach 50 km/h, such as tractors and mopeds, are forbidden from using the expressways. The highest posted speed limit is in some sections of expressways in Central and Eastern Japan. Variable speed limits are also in effect on most expressways and speeds are temporarily reduced due to adverse driving conditions. Many rest facilities such as parking areas (usually only with toilets or small shops) and service areas (usually with many more amenities such as restaurants and gas stations) serve travellers along national expressways. Route numbering On October 24, 2016, the Japanese Ministry of Land, Infrastructure, Transport and Tourism had introduced a new format of route numbering system for national expressways. Expressway route numbers begin with the prefix E or C (for circular route) followed by their respective numbers. Expressway routes are numbered according to the parallel national highway routes; for