Just to demonstrate how beneficial the installation of speed tables are, we need to look at the comparison provided by Town of Vienna. The blue bar is the number of cars before installation of speed table and the green bar is after installation.
The graph on the left is traffic going towards Tyson’s Corner and to the right is traffic going away from Tyson’s. There are 2 categories to concentrate on in these 2 graphs are vehicles going </= 25mph and vehicles going > 30mph.
For Northbound traffic, the number of cars going the speed limit increased from 427 cars in 2005 to 4,011 cars in 2008, 839% increase; cars going >30mph decreased from 3,105 to 351, a 785% decrease.
The same thing is true for Southbound traffic, cars going </= 25mph went from 520 to 3,408, a 555% increase, cars going >30mph decreased from 2,327 to 384, a 506% decrease.
We also believe that the Speed monitors are very effective because it signals to drivers how fast they are going thus adjusting their speed accordingly. There was an increase of 126% from 967 to 2193 cars going </=25mph and decrease of 48% from 2495 to 1285 cars going >30mph.
This video was taken on 10/16/08, at 812am.
Conditions: Dark, Very Cloudy, 63 degrees, some cars have lights on.
As you can see, most cars are not using their brakes because they know if they go 25mph and 30mph, there is no need to use the brakes on a speed table. This video shows how effective speed tables are in enforcing a 25mph zone posted speed limit.
