| | Risk groups | Types of risks | Factor interpretation | Literature source |
| | Political | R1: nonreliability and creditworthiness of public agencies | Government deprivation of the rights of the URT project implementer, including unilateral termination of the existing agreement, expropriation or nationalization of the project assets. | [2, 3, 8, 10] | | R2: mistaken or long-winded public decision-making process | A URT project cannot be implemented as planned due to the government’s inefficient willingness, policy violations, and excessive guarantees. | [2–4, 6, 9] |
| | Private | R3: opportunism risk of private agencies | A URT project company does not perform the contractually agreed or nonagreed responsibilities and obligations because of its own economic interests and brings risks to the project. | [10] |
| | Legal and contractual | R4: immaturity in government policies, laws, and regulations | The implementation of URT project encounters institutional obstacles due to immature government policies, laws, or regulations. | [1–5, 7–10] |
| | Financial and economical | R5: inflation | Inflation may greatly increase wages and prices, which will cause an unpredictable increase in costs of the URT project. | [1, 2, 4–10] | | R6: interest rate fluctuation | Unpredictable fluctuations in interest rates of the central bank affect the income of all parties involved in URT projects, which affects the financing costs. | [1, 2, 4, 5, 9, 10] | | R7: irrational financing structure risk | Different financing structures have different project debt levels. If the financing plan is improper, it will cause capital to cut off, which will seriously lead to overall failure of the project. | [9] | | R8: unavailability of funds | The ability of a company to finance URT projects depends on availability of funds, and this too is a function of time, interest rate, and risk factors, among others. Factors such as these can lead to limited fund availability, necessitating capital rationing. | [2, 3, 5–7, 10] | | R9: high-cost financing risk | An ill-managed URT company cannot maintain normal operations due to capital shortage. When a vicious circle takes shape, banks and shareholders gradually lose confidence in the company, and it becomes difficult for the company to obtain financial support, which further intensifies the degree of capital tension. | [2, 3, 5–10] | | R10: shortage of market returns | Operating income of a URT is often not enough to make up for the cost, resulting in losses for the project company. | [2, 3, 5, 7] |
| | Social | R11: public opposition | A URT project is a complex municipal infrastructural venture with many stops and long lines. The construction and operation process inevitably has an impact on urban residents, competitors, and environment. | [2, 3, 8, 10] | | R12: land acquisition and compensation problem | Before construction of the URT project, government departments lead the process of land acquisition in accordance with the planning scheme. In this process, government departments often have disputes over various interests of the related parties. | [1, 2, 7, 10] |
| | Design | R13: design deficiency | Some potential defects may occur due to the lack of comprehensive consideration in the initial design. Such defects can lead to inconvenience and even unreasonable accidents. | [1, 2, 4, 6, 9, 10] |
| | Construction | R14: construction cost overrun | Actual construction cost of the URT project is often higher than the budgeted price due to construction delays, design changes, rising labor or material prices, etc. | [1, 2, 4, 7–10] | | R15: completion risk | Risk of failing to complete the URT project schedule as planned. | [1, 2, 6, 8–10] | | R16: insolvency/default of subcontractor or suppliers | The subcontractor selected by the project company is unable or unwilling to perform the contractual duties. | [2, 4–6], | | R17: labor risk/industrial relation risk | Disputes arising from enforcement of the laws, regulations or contract of the labor. | [2, 4–6, 10] |
| | Operation | R18: demand/usage risk | Whether the output of the URT project can be successfully transformed into cash inflow through market consumption is fundamentally determined by market demand. The project decision-making needs to be based on scientific market forecasts and a cautious attitude; otherwise, the PPP project of URT operation may fall into difficulties. | [2, 4, 5, 7–10] |
| | Relationship | R19: lack of coordination between stakeholders | There may be a rift between stakeholders, resulting in them not performing or refusing to perform their responsibilities. | [3, 5, 7, 9] |
| | Force majeure | R20: force majeure | Such as war, terrorism, lightning, earthquake, hurricane, flood, typhoon, geological changes, etc. | [1, 2, 4–10] |
| | Uniqueness | R21: uniqueness risk | Only when the URT project can obtain stable income can it attract social investors to actively participate in construction of the project. If there is a competitive project, the actual demand for the URT project will inevitably decrease, thus threatening the life of the project. | [2, 8] |
| | Environmental | R22: environmental risk | Project construction brings environmental pollution risks, such as noise pollution, air pollution, water pollution, or solid waste pollution. These pollutions directly affect the normal life of surrounding residents and endanger people’s health. | [1–5] |
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