the passengers walk up steps into the vehicles. For wheelchairs, a retractable lift or ramp is required to gain access to the vehicle. Low-level platforms Generally about above track level and are used primarily by some commuter rail and light rail and tram/streetcar rail systems. Wheelchairs can board low-floor vehicles directly from the platform, but high-floor vehicles require retractable lifts or ramps. High-level platforms Generally above track level and are used primarily by heavy rail, automated guideway, and some commuter rail lines. Only high-floor vehicles can be used, but wheelchairs can board directly from platforms if vehicle floors are level with the platform. Rail terminology with regard to speed Conventional rail Generally, the speed range for conventional rail is or less. The vast majority of local, regional, and express passenger trains, and almost 100% of freight trains are of this category. Countries that do not make distinction between conventional rail and higher-speed rail can have the maximum speeds of conventional rail up to with the systems that can operate at the speeds higher than that be classified as high-speed rail. For the countries with higher-speed rail classification, the maximum speeds of conventional rail can vary which may go up to such as in Canada. Higher-speed rail Generally, the speed range for higher-speed rail is between and . The higher-speed rail can operate at top speeds that are higher than conventional rail but the speeds are not as high as those in the high-speed rail services. These services are provided after improvements to the conventional rail infrastructure in order to support trains that can operate safely at higher speeds. There is no globally accepted standard in the speed ranges for this classification. Local and regional jurisdictions may have their own definitions. For example, a definition in North Texas has a wide range of speeds between and . A planned construction in Thailand, called medium-speed rail, has the top speeds of . In some cases the term higher speed rail would sound incorrect to define a train travelling below a high speed since higher is greater than high. Therefore, the word higher speed rail would sound correct to refer to a train at a speed between 300 and 500 km/h (i.e. greater than the high speed of 200–300 km/h). High-speed rail Generally, the speed range for high-speed rail is between and . There is no globally accepted standard separating high-speed rail from