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。

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When the traffic demand is too high that ramp metering is not effective anymore, the variable speed limit control is needed to relieve the congestion.

但是当高速公路严重拥挤时，匝道控制不再有效，需结合主线可变限速控制，以缓解交通拥挤。

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Warwickshire Police admit there was an issue relating to the shape of the numerals in the signs but said the variable speed limit signs were fully illuminated and clearly showed what the correct speed limit should be.

BBC: Sign error on M42 motorway may mean speeding let-off