高速公路速率漸變控制策略之研究

Abstract

高速公路主線上，不均質的車流往往造成車流造成壅塞或是壅塞擴大的主要原因。當流量接近公路容量時，車隊中的一些小擾動，就會影響到車流的平順運行，而造成衝擊波的效應，如此便使得後方車流的運行受到干擾，而造成車流壅塞之形成與擴大。因此如果採用適當的速率控制策略來建議駕駛者，使駕駛者趨向以適當的速度行駛，如此即可減少不穩定的情形發生和舒緩衝擊波效應，以達到順暢的交通流。因此，必須去發展一個動態最佳化速限控制模式，能夠使行車效率最大化。 本研究提出一個以巨觀車流模式和連續車流理論為基礎之模式，能在瓶頸路段所造成之壅塞狀況下找出最佳化之動態速限漸變控制模式。主要目標為控制範圍總通過量最大化。此數學模式有五個參數需要以實際資料校估：(1)自由流速，(2)壅塞密度，(3)速度和密度關係之時間推移參數，(4)衝擊波關係之時間推移參數，(5)瓶頸路段下游之邊界流量。 本研究將以國道五號為研究對象，先利用現實資料建立一個國道五號北上路段之模擬路段，為了可重現壅塞情況，本研究先了解並分析其瓶頸路段之道路特性，發現壅塞細部原因為雪山隧道內之禁止變換車道，速限改變及安全間距參數增加，修改上述道路特性後模擬路網即可呈現其壅塞情況，本研究再根據此模擬路段找出模式之校估參數，並確認其控制所需元件，其包括了偵測器和速限可變標誌擺設位置、速限數值的設定模式，控制範圍的選取。 將本研究之模擬路段放入速限漸變控制後，其總通過量增加了19.5%，平均旅行時間減少了8.44%等，顯示此模式的確可以增進在國道五號路網時的績效，隨著流量之增加，雖然績效改善空間減少，但仍有效果存在，顯示本研究之模式對於實際路網應用有其成效。

In the main stream of freeway, the non-homogenous traffic flow is the main reason of congestion or congestion expansion. When the flow is closed to the road capacity, the small disturbance in the platoon will affect the traffic flow smooth run, and cause the shock wave, and then it influences the downstream traffic. Finally it results in the expansion of the congestion. Therefore, if there is the properly speed limit control tragedy to recommend the drivers to drive in the appropriate speed, in order to let the traffic flow reduce the occurrence of instability situation and ease the shock effect in order to achieve smooth traffic flow. Thus, it is essential to develop a dynamic optimal speed-limit control model which can maximize the traffic efficiency. Based on this, this study proposes a macroscopic traffic models and continuity model-based model for dynamic variable speed-limit control under the congestion conditions caused by the bottleneck. The objective is maximizing the total throughput in the control boundary, and there are five parameters in the mathematical model which need to be calibrated by using field data: (1) the free velocity, (2) the jam density, (3) the parameter of the relationship between density and speed over time, (4) the parameter of the shock wave over time, (5) the downstream boundary flow of bottleneck. The freeway No.5 is the research object of this study. Firstly, the study uses the field data to establish the simulation of the northern section of Freeway No.5, in order to reproduce the congestion, for this, this study analyzes the characteristics of bottleneck section of the road, and finds the detail reason of the Hsuehshan Tunnel congestion is the exhibition of land changing, speed limit changes and increase of the safety headway parameters. And this study find out the model calibrated parameters , the car-following factor which is needed by the simulation and the component of the control, which includes the speed limit sign and detector location, and the speed limit value, control boundary selection. This study put the variable speed limit control into the simulation network, and the total throughput increased by 19.5%, average travel time decreased by 8.44%, etc. It shows that this model can indeed improve the performance of the network in the Freeway No.5. With the increasing of the flow, although the performance improvement is reduced, but it still has the effect on the main stream. The result indicates that the model of this paper is effective on the simulation network.