to allow vehicles to travel from one place to another. The most common arrangements are public highways, where appropriately licensed vehicles can navigate without hindrance. These highways are on public land and are maintained by the government. Similarly, toll routes are open to the public after paying a toll. These routes and the land they rest on may be government or privately owned or a combination of both. Some routes are privately owned but grant access to the public. These routes often have a warning sign stating that the government does not maintain the way. An example of this are byways in England and Wales. In Scotland, land is open to un-motorised vehicles if the land meets certain criteria. Public land is sometimes open to use by off-road vehicles. On US public land, the Bureau of Land Management (BLM) decides where vehicles may be used. Railways often pass over land not owned by the railway company. The right to this land is granted to the railway company through mechanisms such as easement. Watercraft are generally allowed to navigate public waters without restriction as long as they do not cause a disturbance. Passing through a lock, however, may require paying a toll. Despite the common law tradition Cuius est solum, eius est usque ad coelum et ad inferos of owning all the air above one's property, the US Supreme Court ruled that aircraft in the US have the right to use air above someone else's property without their consent. While the same rule generally applies in all jurisdictions, some countries such as Cuba and Russia have taken advantage of air rights on a national level to earn money. There are some areas that aircraft are barred from overflying. This is called prohibited airspace. Prohibited airspace is usually strictly enforced due to potential damage from espionage or attack. In the case of Korean Air Lines Flight 007, the airliner entered prohibited airspace over Soviet territory and was shot down as it was leaving. Safety For a comparison of transportation fatality rates, see: Air safety statistics. Several different metrics used to compare and evaluate the safety of different vehicles. The main three are deaths per billion passenger-journeys, deaths per billion passenger-hours and deaths per billion passenger-kilometers. See also Automotive acronyms and abbreviations ISIRI 6924 Narrow-track vehicle Outline of vehicles Personal transporter Propulsion Single-track vehicle Vehicular dynamics Vehicular metrics References Transport Manufactured goods