Public transportation is a large service industry, including buses (large buses/minibuses/small buses), taxis, subways, light rail, ferries, etc., and is the main mode of transportation for citizens' daily travel. With the expansion of cities in my country and the increasing congestion of public transportation, ticketing, ticket checking, and settlement have become a tedious and arduous task for public transportation companies. How to adopt modern methods to adapt to the requirements of modern cities for public transportation systems has become a major issue facing transportation management departments and operating companies. The urban public transportation "one-card" system uses contactless IC cards as the ticket carrier, supported by local area networks and remote networks, and utilizes various electronic payment terminals to automate the processing of billing, collection, statistics, analysis, prediction, decision-making, and central clearing. Passengers can use a single IC card to ride various modes of transportation and pay for parking, tolls, etc. It has gradually become an essential infrastructure in large and medium-sized cities and an important means in the process of urban intelligence and informatization. In the design, implementation and operation of the "One Card" system, there are various unavoidable technical difficulties and management obstacles. If these are not properly addressed in the early stages of system construction, they will leave hidden dangers for the future construction, operation, expansion and upgrading of the system. 1 Technical Principles of the "One Card" System The planning and design of the "One Card" system generally starts at a high level. It is also because of these high starting points that many implementation difficulties have arisen: (1) Fully adopt IC cards that conform to international standards. (2) Adopt flexible and diverse ticketing management mechanisms according to the characteristics of different public transportation operators, such as open operation of bus vehicles with a single ticket, closed/semi-closed operation of subway with distance-based fare calculation and taxi terminal settlement operation, so as to maximize the inclusion of all operating companies and transportation vehicles in the public transportation field into the "One Card" system. (3) Set up complete and flexible billing and charging modes, such as segmented billing, distance-based billing, zoned billing, time-based billing, and route-based billing, so as to maximize the adjustment of passenger flow, optimize urban public transportation resources, and enable all operators to benefit from the implementation of the "One Card" system. (4) Establish a complete system security system to ensure that the system's security and reliability reach the level of the banking system, and ensure that the system's data transactions, collection, transmission and settlement are guaranteed to the greatest extent. (5) Maximize compatibility with existing IC card systems (such as public transport IC card fare management systems) to protect existing investments. 2 One of the difficulties: IC card selection Contactless IC cards exchange data with readers via radio waves. The chip does not need to be exposed, which has a significant advantage over contact IC cards and has become the only choice for "one-card" systems. There are many IC card products on the market. Logic encryption cards, CPU cards or TYPE A, TYPE B standard cards and non-standard cards all have their applications, each with its own advantages and disadvantages. This makes IC card selection the most controversial, time-consuming and troublesome issue for owners and system integrators in the early stages of system construction. Currently, the main IC card products used in global "all-in-one" systems include Mifare™ products compliant with ISO/IEC 14443 Type A standards, CPU-integrated products compliant with ISO/IEC 14443 Type B standards, SONY products that do not conform to ISO/IEC 14443 standards, and LEGIC™ products that do not conform to ISO/IEC 14443 standards. Among these, the Mifare™ series products (especially the encrypted logic card MF1) from SONY have the most applications and the largest number of cards issued. SONY's products are currently used in the Octopus card system in Hong Kong, and the All-in-One Card system in Singapore and Shenzhen. Although the number of applications is not large, it has set a record for the largest number of cards issued in a single transaction. Products compliant with ISO/IEC 14443 Type B standards are considered the future direction of contactless CPU cards, but market promotion has been difficult so far, and the number of cards issued is very limited. LEGIC™ products are currently only used in Shenzhen, and the number of cards issued is small. This is also the first time this product has been used in a payment system. The following points should be noted when selecting IC cards: (1) Compliance with international standards IC cards are products that only appeared in the 1990s. Due to their good market prospects, many large and powerful companies in the world have invested a lot of manpower and resources to develop related products. However, they are technically independent, keep secrets from each other, and are incompatible with each other, which makes it very difficult for users to choose products. Although the international standard for IC cards, ISO/IEC 14443, has been established, there are still two different versions of the standard, Type A and Type B. Moreover, the ISO/IEC 14443 standard itself is still being developed and improved. Nevertheless, when choosing products, you should try to choose products that comply with the standard. You must be very careful when choosing which standard to use to ensure that the selected product is a mainstream product, thereby protecting the long-term interests of investors. (2) High security and reliability Since the "one-card" system adopts the stored value charging method, the card not only stores the cardholder's information, but also records the cash information deposited by the cardholder. Its security and reliability are particularly important. Once the data in the card is illegally modified or a counterfeit card appears, the interests of investors and cardholders will be lost. Similarly, if the card is not reliable and data errors or loss occur, or even if the card fails, the lack of good remedial measures will cause economic losses to users and investors. (3) Advanced technology Although IC cards have not been around for long, technological improvements and new technologies have emerged quite rapidly. Therefore, choosing products with technological advantages is undoubtedly a necessary consideration to protect the interests of investors, and it is also a sign of the system's advanced nature. (4) Adopting mainstream technology IC card technology is in a period of rapid development. Various companies' products and technologies are engaged in fierce competition. The result of the competition will be that products with advanced technology, better performance-price ratio, and in line with development trends will stand out and become the dominant products in the market and form mainstream technologies. Choosing products that conform to development trends is extremely beneficial to the future supply, price, and service of the products. (5) Products with technological continuity Choose products with technological continuity, that is, subsequent products can be compatible with the technology of earlier products and form a series of products. This is the basis for the upgrade and application expansion of the "one-card" system. (6) Mature Products The “One-Card” system is open to the general public, and IC cards are publicly issued. If IC cards need to be recalled due to card or system reasons, in addition to the huge workload and economic losses that are difficult to make up for, it will also deal a fatal blow to the public’s confidence in using the cards, and seriously affect the reputation and subsequent promotion of the “One-Card” system. The consequences of immature products are unimaginable. Therefore, it is necessary to select products that are technically mature and have successful application cases. (7) Stable Supply After the “One-Card” system is put into operation, the procurement of IC cards will continue. If there is no stable supply and supply difficulties occur, it will have a huge impact on the investment benefits of the system and will also easily cause public dissatisfaction. (8) Competitive Products Competitive products are very beneficial to users. Products from multiple manufacturers can be supplied, the supply can be reliably guaranteed, and it is also easy to obtain more favorable procurement prices. (9) Economical Prices In order to reduce the investment pressure of the system, enhance cardholders’ care for the cards, and reduce the large-scale loss of cards, the “One-Card” system generally adopts the deposit rental method, that is, cardholders first pay a deposit equivalent to the cost of the card to obtain the right to use the IC card. Therefore, whether the card is economical, whether it can be accepted by the general public, and whether it can help expand the number of cards issued are key factors for the successful implementation of the system. (10) Solution of single-journey tickets for subway/light rail The “one-card” system also has a very special problem: single-journey tickets for subway/light rail/ferry. Single-journey tickets involve small amounts, are anonymous, and cannot be reported lost, making their selection and design quite difficult. From the perspective of simplifying ticketing operations and management, it is best to use disposable tickets, that is, the ticket card is not collected when the passenger exits the station. However, the price of any contactless IC card on the market is higher than the lowest ticket price for subway/light rail/ferry in China. This poses a risk that IC card single-journey tickets may be illegally purchased and lost in large quantities. In addition to using low-priced IC cards as much as possible, an effective solution is to reduce the cost of each use by recycling single-journey tickets. Regardless of the type of ticket card used, compatibility with stored-value cards must be considered, as it is not easy to install two sets of reading and writing equipment on the same ticket checking equipment. To clearly distinguish single-journey tickets from stored-value cards in appearance, they are often packaged as non-standard narrow strip cards or round, chip-like cards. When selecting tickets, in addition to considering technical compatibility with stored-value cards, a comprehensive understanding of chip supply, antenna shape, packaging equipment, packaging costs, and the technical specifications of related equipment such as automatic ticket gates and vending machines is necessary. The existence of IC card standard issues objectively places higher demands on system openness. Ideally, a universal system compatible with TYPE A, B, and the future TYPE C standard, applicable to all IC cards, should be established, allowing the system to adapt to different occasions and user requirements after its launch. In reality, to date, no IC card or reader compatible with all standards has been developed; only products compatible with TYPE A and B or TYPE B and C are available. Furthermore, economic feasibility is also an unavoidable issue. 3. Second Challenge: System Compatibility Currently, many cities have already implemented IC card fare management systems for public transportation (mainly buses) and automatic fare collection (AFC) systems for subways. The construction of a "one-card system" must first address the integration and smooth transition between the old and new systems. It's an undeniable fact that issuing IC cards can generate substantial returns. All relevant government departments across various sectors are eager to establish their own IC card systems, with bus companies, rail companies, and settlement banks all directly profiting. Taking a medium-sized city's bus IC card system as an example, assuming 300 IC cards are installed on vehicles, data collection points are set up at 14 bus terminal stations (3 of which offer IC card issuance and recharge services), and 30,000 IC cards are issued, the project investment is approximately RMB 2.2 million. This is a one-time investment, and the entire investment can be recovered in less than three years after the system is officially operational. Afterward, it will bring the bus company approximately RMB 900,000 in direct revenue annually. If the system is expanded into a public utility "one-card" management system in the future, and the system's settlement center becomes the settlement management center of the "one-card" system, serving as the center for card issuance, equipment authorization, and transaction clearing, an additional RMB 500,000 in revenue will be generated. By issuing a massive number of IC cards, card-issuing institutions not only gain existing economic benefits (such as IC card deposits, funds accumulated from damaged or lost cards, and advertising revenue), but also firmly control the rights to future business expansion, technological updates, and business model adjustments within the entire industry. The "One-Card System" centralizes card issuance rights in the settlement management center, depriving existing card-issuing companies of their right to continue issuing cards. This not only causes card-issuing companies to lose their vested interests, but also means that if existing systems are incompatible with the "One-Card System," those systems will be gradually phased out, and existing investments (mainly IC cards and terminal equipment such as vehicle-mounted machines and ticket gates) will be difficult to recoup. Therefore, without a proper solution to the system compatibility issue (substantial redistribution of benefits), the implementation of the "One-Card System" will inevitably provoke strong resistance from these companies and their superiors. The construction of the "One-Card System" not only involves complex technology, but also faces unavoidable practical problems under market economy conditions, such as initial system investment, profit distribution, and risk-sharing. This is the underlying reason for the long-standing difficulties and obstacles in the implementation of the "One-Card System." 4. The Third Challenge: Project Coordination. The construction of the "One-Card System" is a complex technical issue, and even more so, a completely new management problem, involving the vital interests of all participating units. Because the "One-Card System" adopts the world's most advanced high technology and a completely new operation and management model, it is entirely new to the public transportation industry's regulatory authorities, operational leaders and employees, and passengers. How to correctly understand and become familiar with this system is a crucial issue, directly related to its promotion and application. The system's construction involves all urban public transportation operating units, which generally have complex relationships involving multiple departments, owners, and types of entities. These include state-invested operations, joint investments by national and local governments, and independent investments and operations by foreign-invested and private enterprises. Faced with the intricate web of interests among various units and departments, government departments must adopt a systems engineering approach to coordinate and streamline the vested and long-term interests of all parties, take the lead in organizing the implementation and promotion of the project, and, when necessary, use administrative means to regulate the responsibilities and behaviors of each participating unit. In addition, corresponding supporting policies must be formulated in areas such as transportation policy guidance, administrative supervision, transportation planning, investment and financing, and fiscal and tax support to support the public transportation industry, leverage the significant advantages of the "one-card" system, and fully embody the strategic concept of "public transport priority." Various regions have generally adopted the approach of establishing independent economic entities such as "one-card" companies, with public transport operating companies participating in project construction and operation through equity investment, hoping to resolve the thorny issue of profit distribution through market-based means. Even so, appropriate intervention by government departments is still indispensable. 5. Conclusion The informatization, networking, and intelligentization of public transportation systems are the current development direction of urban transportation. This involves technologically transforming traditional public transportation systems through information technology, intelligent control technology, and IC card technology, improving the service and management levels of public transportation systems, and technically guaranteeing the development strategy of "public transport priority." Undoubtedly, the implementation of the urban public transportation "one-card" system has very practical significance, but how to solve the aforementioned difficulties and problems is a topic that owners, system integrators, operating companies, and industry experts and scholars need to calmly consider and deeply explore.