In order to improve the performance of the signalized intersection, an unconventional scheme tandem design ( TD) is proposed. A simulation experiment is conducted to evaluate the capacity and delay under the unconventional scheme and two conventional lane assignment schemes. First, the VISSIM is employed as microsimulation to obtain the delay of different designs at signalized T-intersections under different conditions of traffic flow and turning proportion. Secondly, a method based on discriminant analysis (DA) is proposed to determine the best design scheme using the flow and turning proportion as inputs. Finally, a case study in Changsha city, China is used to demonstrate the efficiency and accuracy of these findings. The results indicate that the traffic flow and turning proportion are the crucial factors in scheme selection of lane assignment. Different from the previous research, the TD has better performance over various traffic flow levels. Furthermore, a proper proportion of left turns makes TD an outstanding option, which can reduce the delay and decrease the average number of stops and queue length significantly. However, the proportion should not be too high or too low. The research results can help practitioners obtain a quantitative view of appropriate design schemes at signalized intersections when trying to relieve traffic congestion according to different traffic conditions.