|
|
|
|
|
Surface
friction is measured on the complete WSDOT route system every two years.
In essence, a
coefficient of friction is measured via a locked-wheel towed trailer between a tire and
the pavement surface (the actual value is called Friction Number). Vehicle speed is
maintained while water is applied to the pavement surface in front of the test wheel and a
brake is applied to the test wheel. When the test wheel stops rotating (locked-wheel
state), the drag and load (horizontal and vertical force) are measured.
The friction of
most dry pavements is high. Wet pavements are the problem. Thus, the Friction Number
testing process involves application of water to the pavement surface prior to
determination of the friction value. Such data allows WSDOT to identify potential low
friction pavements that in conjunction with accident history and roadway geometrics are
used to minimize wet weather skidding accidents. |
|
Friction Tester
|
|
