Fixed-time signal control is widely used in the real world due to its low cost of implementation. Repeated signal cycles with the same phase structure are applied in the existing fixed-time signal control schemes. However, such signal schemes do not always achieve the best performance, especially when traffic demand is unbalanced. The inclusion of sub-cycles in one cycle provides a potential solution in this situation. This study proposes a time-slot based signal scheme model with a generalized cycle structure for fixed-time signal control at isolated intersections. The proposed signal scheme can generate sub-cycles with different phase structures. It optimizes the number of sub-cycles in one cycle as well as the phase sequence, cycle length, and green splits in each sub-cycle. Certain phases may be skipped in partial sub-cycles. Nonlinear programming models are formulated to minimize average vehicle delay and maximize intersection capacity for under- and over-saturated demand. Solution algorithms for the two nonlinear models are developed by solving a series of mixed-integer-quadratic-programming (MIQP) models and mixed-integer-linear-programming (MILP) models, respectively. The numerical studies validate the advantages of proposed signal scheme in terms of intersection capacity and average vehicle delay. The sensitivity analyses show that: 1) a long maximum green time can enable the conventional dual-ring, eight-phase structure to handle unbalanced demand from the perspective of intersection capacity; 2) the time-slot number of 6 or 7 is suggested considering both the solution optimality and the model complexity.

固定时间信号控制由于实现成本低而在现实世界中被广泛使用。在现有的固定时间信号控制方案中，将使用具有相同相位结构的重复信号周期。但是，这种信号方案并不总是能达到最佳性能，尤其是在流量需求不平衡时。在这种情况下，将子循环包含在一个循环中提供了一种可能的解决方案。这项研究提出了一个具有广义周期结构的基于时隙的信号方案模型，用于隔离路口的固定时间信号控制。所提出的信号方案可以产生具有不同相位结构的子周期。它优化了一个循环中的子循环数，以及每个子循环中的相序，循环长度和绿色分割。某些阶段可能会在部分子周期中被跳过。制定了非线性规划模型，以最大程度地减少平均车辆延迟，并最大程度地满足需求不足和过饱和的路口通行能力。通过分别求解一系列混合整数二次编程（MIQP）模型和混合整数线性编程（MILP）模型，开发了两种非线性模型的求解算法。数值研究验证了提出的信号方案在交叉路口通行能力和平均车辆延误方面的优势。灵敏度分析表明：1）从交叉路口通行能力的角度来看，较长的最大绿灯时间可使常规的双环八相结构处理不平衡的需求。2）建议同时考虑解决方案最优性和模型复杂性的时隙数为6或7。