目前交通感應式匝道儀控中最常應用的方法皆有其缺點，例如需求容量控制法、占有率控制法皆有容量決定及車流均質假設的問題。另一種觀念為使用回饋補償方式能避免容量決定上的困擾，例如ALINEA方法。但是本研究發現ALINEA法仍延續著容量理論的觀念，無法避免容量理論中均質的缺點，仍假設在很短的感應時間下車流保持固定的到達率，依此做為下一個控制時段的流量預測。但實際流量並非如此，因此，本研究考量實際車流不均質與隨機到達特性，採用布朗運動理論將隨機車流模型、即時密度變異數納入匝道儀控控制邏輯中，來研發出一種新的匝道儀控方法，稱為穩定法。可以預測在相同交通狀況下由於車流本身之不均特性引發未來發生擁擠的時間，以決定主線下游回饋之目標密度，將車流狀況控制在最佳的目標密度下。利用模擬測試結果顯示，採用本方式在主線下游密度保持在臨界密度下兩個密度標準差之下，可比AL的EA法以臨界密度為目標密度的匝道儀控法為佳。

Convention alramp metering methods always have some weaknesses in the estimation of capacity, such as demand-capacity method and occupancy metering method. They usually assume that the traffic flow is homogenous and determine the metering rate with preset capacity. ALINEA method improves the capacity estimation by feedback concept of occupancy, but it is also under the assumption of homogenous capacity. In a short control period, it assumes the arrival ratio is the same with the average and depends on it to predict the volume of next control period. In fact, practical traffic does not follow in that way. In view of the stochastic feature and unstable phenomenon especially when traffic becomes heavy, a new concept of ramp metering is developed in this paper based on the predicted instability of density detected on the downstream from the ramp. According to the simulation results using the new density stability concept method maintaining density 2 standard variations less than the critical density can prevent congestion and produce more throughputs on the ramp. The method developed in this paper is then called density stability ramp metering method.