- by Jennifer Evans for Expatica

A variable speed limit test on the A12 motorway between The Hague and Arnhem will begin this week in an effort to improve traffic flow, the Dutch Traffic Ministry reported Thursday.

The test, to take place between Bodegraven and Woerden, will allow speed limits to be changed at any moment due to incidents such as heavy rain and traffic. Speed limits will vary from 60 to 120 kilometres per hour.

For example, the speed limit will be decreased during heavy rain, after a rain, and when rain is anticipated to prevent traffic accidents caused by wet roads and poor visibility, according to nu.nl. The Traffic Ministry's road and canals authority (RWS) will use weather reports from KNMI, the national weather centre.

Text displays located above the A12 will alert drivers to the current speed limit.

Harmonica
RWS will monitor the number of traffic accidents and queues during the variable speed limit test to determine its impact on the so-called 'harmonica-effect.'

The harmonica-effect occurs when drivers must slam on their brakes in traffic, and then slowly build back up to moderate speed. The pattern can repeat itself several times during a traffic jam, and negatively affects the flow of traffic.

Earlier tests
Variable speed limit tests were undertaken on the A1 near Bussum, where the speed limit was raised during normal traffic periods to reduce travel time. A test was also completed on A58 near Tilburg, in which the speed limit was lowered to improve air quality.

A test will begin on the A12 near Voorburg later in 2009. Yet another test will begin on the A20 near Rotterdam in 2010.

On a Dutch motorway (FlickR/Kemas Junius Antonius)