Abstract: This paper defines various types of urban rail transit systems based on transportation capacity, speed, and cost, and elaborates on the development direction of urban rail transit in China in light of the current urbanization level. Keywords: Urban rail transit; road network planning; traffic classification; localization 1 Introduction Since the reform and opening up, China's urban scale and economic construction have developed rapidly, the urbanization process has accelerated, and the urban population has increased dramatically. There are now 34 large cities with a population of over 1 million, including 8 with over 3 million. During peak passenger periods in these large cities, passengers are highly concentrated and flow in roughly the same direction. Low-capacity transportation tools are far from meeting the needs of the public. Adopting urban rail transit systems and developing a multi-level, three-dimensional, and intelligent transportation system is one of the important strategic measures to fundamentally improve traffic demand. 2 Goals of Urban Rail Transit Construction and Development in China The transportation system of a modern city should, on the basis of meeting the needs of the vast majority of people, be highly coordinated with the urban development layout, and combine long-term planning goals with short-term adjustments and improvements. In China, in the near term, a road network system should be established that is basically compatible with urban traffic volume. The service management quality of conventional public transportation should be gradually improved, and comprehensive transportation planning should be organically integrated to expand space utilization. The focus should be on developing a public transportation network with rail transit as its backbone, actively introducing subway and light rail transit modes with large and medium passenger capacities to meet the needs of sustainable urban development. China's urban rail transit is still in its initial development stage. The goals should be comprehensive planning, optimized layout, rational allocation of resources, environmental protection, convenience and speed, adaptation to local conditions, and moderate cost. 3. Selection Principles of Urban Rail Transit Systems In today's world, subways, light rail, central or side-guided rubber-wheeled new transportation systems, fully suspended aerial trains, linear locomotives, straddle-type monorail systems, and maglev trains—both mature and still in the experimental stage—are diverse. Figure 1 shows the major urban rail transit systems currently in operation and under development worldwide; Table 1 shows the performance indicators of various rail transit systems. Currently, China's operational, planned, and under-construction rail transit systems generally include trams, light rail, subways, monorails, and urban expressways. Table 1 provides a reference table for the transport capacity and travel speed of rail transit systems. The selection of an urban rail transit system should be based on the road network plan, referring to the data in Figure 1 and Table 1, considering factors such as transport capacity, travel speed, and cost to choose an appropriate form. 4. Adaptability of Various Urban Rail Transit Systems 4.1 Trams Trams have a transport capacity of 2,000–1,500 passengers/hour and a transport speed of generally 15–20 km/h. They operate in combination with other modes of transportation, and their capacity is relatively limited. They are only preserved as scenic features in a few cities like Dalian and are not suitable for widespread adoption. 4.2 Light Rail Transit Based on the analysis of urban conditions in China, it is generally believed that for large cities with a population of 1 million–2 million, with peak-hour passenger flows of 20,000–30,000, equipping them with light rail transit systems can meet the needs of public transport. Light rail transit can have dedicated lanes or run on the surface in conjunction with other modes of transportation. It is mostly built along the urban road network, only transitioning underground or elevated at busy intersections or sections. Compared to subways, it is cheaper, easier to construct, has a shorter construction period, and yields faster results. Light rail transit systems are suitable for small and medium-sized cities in my country. 4.3 Underground Railways: For megacities with a population exceeding 2 million and peak-hour passenger flows often exceeding 40,000, passenger transport requires high-capacity subways, supplemented by light rail networks. Within urban areas, subways mostly run in underground tunnels, with stations also underground. In suburban areas where environmental conditions permit, surface or elevated lines can be used as much as possible to save investment. Subway systems must have dedicated lanes and be fully enclosed. Its drawbacks include high investment costs, difficult construction, long operating periods, and slow returns. Subway construction should only be considered when a city's economic development reaches a relatively high level. Currently, only Beijing, Shanghai, Tianjin, and Guangzhou in my country have subways. 2.4.4 Rubber-tired rail systems are elevated rail transit systems that run on dedicated tracks, not occupying ground-level road space. They feature low vibration, low noise, high climbing ability, small turning radius, lower investment (the cost of 1 km of subway can build over 3 km of elevated railway), and faster construction speed than subways. Current monorail, new railway transportation systems, and VAL systems all use rubber-tired systems. Monorail transport capacity is 6,000–20,000 passengers/hour; Chongqing's monorail line is being imported from Japan. New transportation systems are developed based on railway and highway systems, with passenger capacity of 5,000–150,000 passengers/hour; currently, this is not yet available in my country. Urban rapid transit is an ideal transportation system between cities and suburbs or satellite cities, with large transport capacity, high speed, and travel time generally not exceeding 30-45 minutes. Outside the city center, it is entirely built at ground level; within the city center, it has dedicated lanes or partially elevated and partially underground sections, making it less expensive than subways. 5. Construction Standards and Localization of Technology and Equipment Modern urban rail transit systems reflect the application level of today's high technology. Given China's relatively limited economic resources, acquiring high-standard urban rail transit systems at exorbitant costs is not advisable. Currently, the focus should be on developing China's rail transit industry based on mature technology, ease of localization, suitability for mass passenger transport, and meeting the requirements of safety, economy, speed, and appropriate comfort. Beijing, Tianjin, Shanghai, and Guangzhou all have operational rail transit lines, and significant progress has been made in the technological advancement and localization of equipment for underground railways. However, a large amount of technology and equipment is still imported wholesale from a few developed countries. Often, relying on loans from a particular country necessitates purchasing equipment from that country, resulting in inconsistent equipment standards and varying equipment across cities, making unified management difficult. Furthermore, prices remain high (9-10 times that of domestically produced equipment), sometimes accounting for over 60% of the entire rail transit construction, exceeding any previous civil engineering project, severely hindering the overall development of China's rail transit industry. To change this situation, we should adhere to the principle of "combining technology and trade," systematically and organizedly digesting and absorbing advanced foreign technologies, striving to expand the localization of rail transit technology and equipment, continuously increasing the domestic production rate, minimizing the impact of foreign loans, and enabling China's rail transit industry to embark on a path of rapid development. 6. Conclusion Vigorously developing the rail transit industry is a fundamental national policy of China and a basic strategy for major cities to achieve sustainable development. During the "15th Five-Year Plan" period, the national plan for investment in urban rail transit reached 800 billion RMB. Clearly, this presents a historic opportunity for the development of urban rail transit within the broader context of meeting the challenges of the WTO and striving to build my country into a moderately developed country as soon as possible. It is foreseeable that urban rail transit will play a crucial and irreplaceable role in the internationalization of my country's major cities. How to appropriately develop my country's urban rail transit system involves many policy and technical issues that require research. Only through thorough research and demonstration, comprehensive planning, meticulous design, and the rational assimilation and adaptation of foreign technologies can an urban rail transit system suitable for China's national conditions be established, thus avoiding the painful consequences of the current extensive development model.