Traffic signal control has always been the core problem of urban traffic control, in order to propose a more efficient signal intersection control method, this paper abstracts the signal intersection queue vehicle dissipation and waiting problem into a class of finite-time stability (FTS) problems for switching positive systems containing unstable subsystems. A new dwell-time dependent co-positive Lyapunov function (DTDCLF) is introduced, which can effectively solve the analysis of dwell-time dependent problems and can more effectively use the switching rule to construct the Lyapunov function. Sufficient conditions for the FTS of switched positive systems containing unstable subsystems in discrete-time and continuous-time contexts are obtained by this method, respectively. Lastly, an illustrative numerical example is presented to showcase the efficiency of the method. The method outlined in this paper provides a more efficient solution to the signal timing problem at oversaturated intersections, allowing vehicles at oversaturated intersections to be evacuated more quickly, reducing traffic delays and improving intersection efficiency.