当城市交通需要穿越江河海湾时，通常是在桥梁与水下隧道方案之间做出选择。从工程的造价、耐久性、安全、生态环境和社会效益等角度，通过对水下隧道与桥梁渡越方案的分析、对比和论证，得出采用水下隧道方案穿越江河海湾相对桥梁具有较大综合优势的结论。水下隧道的优越性主要在于:运营期间不影响水路航运；不受恶劣气候的影响，保证交通全天候正常通行；占地少，拆迁量小；能保护原有水域自然风光；可有效安排各种市政管道穿越水域；具有很强的抵御自然灾害和战争破坏能力。

Where urban traffic infrastructures crossing rivers or gulfs are to be built, it is common to make decisions between the bridge alternative and the underwater tunnel alternative. The article makes analysis and comparison on the bridge alternative and the underwater tunnel alternative in terms of construction cost, durability, security, ecological and environmental impacts and social efficiency, which concludes that the underwater tunnel alternative has more comprehensive advantages than the bridge alternative. The underwater tunnel alternative has the following advantages: the waterway transportation will not be affected during the operation of the tunnel; the traffics through the tunnel will not be affected by bad weathers and allweather transportation can be guaranteed; less land occupation and less existing infrastructure dismantling; the original natural scene of the water area can be reserved; the municipal pipelines crossing the rivers or gulfs can be installed effectively; higher capacity against natural disasters and wars.