In 2005, the city of Bellevue, WA, assembled information from the previous 5 years testing radar speed signs at a range of locations. Not only did the report strongly show that these signs do reduce speeds and often remain effective even after 4 years of use in the same spot, they also recommended some reasons which explain why some signs aren't as effective and may not provide good traffic slowing effects. While this is not the fault of the signs themselves, it would seem to be the choice of sign location.
They learned that the signs that didn't have much of an effect were the ones that had the most limited sight-distance for oncoming traffic. A driver can't be slowed by a signal she can't easily see. While this is straightforward common sense, it really seems that one similar circumstance among ineffective signs was that they weren't clearly visible from 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 prompted the recommendation that the community continue to install radar speed signs for traffic control, and listed several issues so far as placement to help the community make the most use of this valuable traffic taming tool.
They learned that the signs that didn't have much of an effect were the ones that had the most limited sight-distance for oncoming traffic. A driver can't be slowed by a signal she can't easily see. While this is straightforward common sense, it really seems that one similar circumstance among ineffective signs was that they weren't clearly visible from 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 prompted the recommendation that the community continue to install radar speed signs for traffic control, and listed several issues so far as placement to help the community make the most use of this valuable traffic taming tool.
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A speed display sign that's not placed in the right area won't be as useful as it probably should be. Let the experts at trafficalmsystems.com help you determine which traffic calming devices are best for your neighborhood.
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