The length design of the acceleration lane depends on not only traffic speed but also traffic volume of the main line and ramp of expressway interchanges.
高速公路加速车道的设置长度不仅取决于主路及匝道的设计速度，还与主路及匝道的交通量有关。
2
Therefore, an effective combination of ramp metering and variable speed limit control is important to achieve a good performance.
由此，匝道调节率与可变速度限制间高效的联合控制对于提高道路性能显得尤为重要。
3
It has four start mode: the ramp voltage start, the limit current start, the rampspeed start and the discrete frequency start.