The significant rise in the number of motor vehicles and the increased utilization of land in China has led to the emergence of numerous large-scale parking facilities, resulting in exacerbated congestion at their entrances and exits. To address this issue, it is essential to first establish criteria for assessing congestion. This study employs an average delay model for various vehicle types and takes into account the distribution ratios of incoming vehicles across different lanes. Through quantitative analysis, the research identifies the causes and severity of congestion for different vehicle categories at parking lot entrances and exits. The findings aim to inform effective management and regulation of traffic flow in these critical areas.