Each country has its own unique way of dividing up the responsibility for enforcing all the
laws mentioned above. In nearly all countries, though, the laws controlling
driving in practice (like speed limits) are enforced by the police, who are in the best position to identify violations as they occur and to issue citations or make arrests.
Some countries, like Australia, prefer to put everything road-related into a single agency at the state level. Thus, in the Australian state of New South Wales, the
Roads and Traffic Authority (RTA) is responsible for driver
licensing; highway construction, maintenance, and
patrol; and many other things. Policing on Australian roads is provided by the relevant state police.
In contrast, in the United States, many U.S. state governments have a
Department of Transportation that
handles road construction and maintenance (subject to some guidance from the federal Department of Transportation), and a separate Department of Motor Vehicles that handles driver licensing and vehicle registration. There is usually a state police agency (called the Highway Patrol or Department of Public Safety) which enforces driving laws on state highways. On local roads, driving laws are enforced by county sheriff''s departments or city police departments.
Except for a few jurisdictions, bicyclists are legally treated as drivers of vehicles and expected to cycle vehicularly. Drivers of bicycles are almost never subject to licensing. However, some municipalities do require permits for bicycles.