Motorway off-ramp is a main source of traffic congestion and collisions. Heavy diverging traffic and associated lane changing to off-ramp slows down the mainline traffic speed. When the off-ramp queue spills onto the motorway mainline, it may cause a major breakdown of the motorway capacity and a significant threat to the traffic safety. This paper proposes using Variable Speed Limits (VSL) to protect the motorway off-ramp queue to improve safety in congested diverging areas through microsimulation tests. To support timely activation of VSL in advance of queue spill-over, a proactive strategy is proposed based on off-ramp queue estimation and new arrival prediction in the near term. This process determines the estimated queue size on the off-ramp in the near-term, on which the decision to change speed limits is made. VSL can effectively slow down traffic as it is mandated and enforceable in Queensland, Australia. As a possible scenario, reduced speed limits could make drivers more attentive to the surrounding condition, and prepared for a sudden braking of the leading car. This paper analyses and quantifies this possible effect of VSL on traffic safety and efficiency using the microsimulation approach.

中文翻译：

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高速公路出站队列保护的可变速度限制

高速公路出口匝道是交通拥堵和碰撞的主要来源。大量的分流交通和相关的车道变更到出口匝道减慢了主线交通速度。当匝道外排队涌入高速公路主干线时，可能会导致高速公路通行能力的严重崩溃，并对交通安全构成重大威胁。本文提出使用可变速度限制 (VSL) 来保护高速公路出口匝道队列，以通过微观模拟测试提高拥挤分流区域的安全性。为了在队列溢出之前及时激活 VSL，提出了一种基于出站队列估计和近期新到达预测的主动策略。此过程确定近期出口匝道上的估计队列大小，并据此做出更改速度限制的决定。VSL 可以有效地减缓交通，因为它在澳大利亚昆士兰州是强制性的和可执行的。作为一种可能的情况，降低速度限制可以使驾驶员更加注意周围的状况，并为前车的突然刹车做好准备。本文使用微观模拟方法分析和量化了 VSL 对交通安全和效率的这种可能影响。