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Minnesota Department of Transportation
The Smart Work Zone Speed Notification (SWZSN) system aims to alleviate congestion; queuing; and rear end crashes in work zones by informing drivers of the speed of the downstream segment using a type of portable Intelligent Lane Control System (ILCS); Portable Changeable Message Signs (PCMS). The hypothesis was that drivers; knowing the speed up to 1 mile downstream; will slow down early or at least be alert and perform smoother decelerations. Video of the SWZSN was analyzed over two years of operation by the Minnesota Traffic Observatory. Overall; the system resulted in beneficial reductions of selected decelerations by the drivers. In situations where the messages communicated to the drivers were consistent and accurate; reductions of more than 30% in the selected deceleration rates were observed. Unfortunately; there were several cases where counterproductive or misleading messages were communicated to the drivers; prompting relative increases to the selected deceleration rates. The most important observation; stemming from both positive and negative influences; was that the speed notification system was noticed by drivers and resulted in a statistically significant influence on driving behavior; unlike other driver alert systems.
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