sections. Alternative methods of motive power include magnetic levitation, horse-drawn, cable, gravity, pneumatics and gas turbine. Passenger trains A passenger trains stops at stations where passengers may embark and disembark. The oversight of the train is the duty of a guard/train manager/conductor. Passenger trains are part of public transport and often make up the stem of the service, with buses feeding to stations. Passenger trains provide long-distance intercity travel, daily commuter trips, or local urban transit services, operating with a diversity of vehicles, operating speeds, right-of-way requirements, and service frequency. Service frequencies are often expressed as a number of trains per hour (tph). Passenger trains can usually can be into two types of operation, intercity railway and intracity transit. Whereas intercity railway involve higher speeds, longer routes, and lower frequency (usually scheduled), intracity transit involves lower speeds, shorter routes, and higher frequency (especially during peak hours). Intercity trains are long-haul trains that operate with few stops between cities. Trains typically have amenities such as a dining car. Some lines also provide over-night services with sleeping cars. Some long-haul trains have been given a specific name. Regional trains are medium distance trains that connect cities with outlying, surrounding areas, or provide a regional service, making more stops and having lower speeds. Commuter trains serve suburbs of urban areas, providing a daily commuting service. Airport rail links provide quick access from city centres to airports. High-speed rail are special inter-city trains that operate at much higher speeds than conventional railways, the limit being regarded at . High-speed trains are used mostly for long-haul service and most systems are in Western Europe and East Asia. Magnetic levitation trains such as the Shanghai maglev train use under-riding magnets which attract themselves upward towards the underside of a guideway and this line has achieved somewhat higher peak speeds in day-to-day operation than conventional high-speed railways, although only over short distances. Due to their heightened speeds, route alignments for high-speed rail tend to have broader curves than conventional railways, but may have steeper grades that are more easily climbed by trains with large kinetic energy. Their high kinetic energy translates to higher horsepower-to-ton ratios (e.g. ); this allows trains to accelerate and maintain higher speeds and negotiate steep grades as momentum builds up and recovered in downgrades (reducing cut, fill, and tunnelling requirements). Since lateral forces act on curves, curvatures are designed with the highest possible