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| When Radar Signs Don't Help |
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In 2005, the community of Bellevue, WA, collected data from the past 5 years of tests radar speed signs at a collection of locations. Not only did the report strongly suggest that these signs do reduce speeds and typically remain effective even after 4 years of usage in the same spot, they also suggested some reasons why some signs are not as effective and may not provide good traffic speed reduction effects. While this isn't the fault of the signs themselves, it appears to be the selection of sign location.
In 2005, the community of Bellevue, WA, collected data from the past 5 years of tests radar speed signs at a collection of locations. Not only did the report strongly suggest that these signs do reduce speeds and typically remain effective even after 4 years of usage in the same spot, they also suggested some reasons why some signs are not as effective and may not provide good traffic speed reduction effects. While this isn't the fault of the signs themselves, it appears to be the selection of sign location. They found that the signs that didn't have much of an effect were the ones that had the most limited sight-distance for approaching traffic. A driver can't be influenced by an indicator he or she can't clearly see. While this is simple common-sense, it appears that one shared trait among the signs that didn't work was that they weren't visible very far away. Signs that are approached at a high speed and do not become clearly observable until the driver is nearly on them do less for traffic slowing than those the driver can see further away, regardless of if it's far enough back the sign does not yet display that driver's speed. At least 300 feet of high visibility was determined a good amount for effective use of the signs. The least effective signs were also the ones put in places where fewer drivers sped to begin with. When about 85 percent of drivers in that area were already following the posted speed limit, the velocity reductions were much less. This makes good sense, since drivers are already generally careful with their speed in those areas. Speed changes were much more dramatic in places where drivers sometimes exceeded the limit. The study inspired the recommendation that the town continue to install radar speed signs for traffic control, and listed a few considerations so far as placement to help the town make the most use of this valuable traffic control tool. About the Author: A speed display sign that is not placed in the right area may not be as effective as it could be. Let the pros at trafficalmsystems.com assist you in determining which traffic calming devices are best for your community. |