The site bestwelsnel.nl taps into the National Data Warehouse for Traffic Information (NDW) to bring you the top speeds registered on Dutch motorways.
The NDW registers speeds using over 24,000 detection loop pairs spaced 2.5 metres apart. Bestwelsnel.nl (the name means ‘quite fast’) displays three types of speeds: unconfirmed top speeds (grey), daily confirmed top speeds (green) and confirmed top speeds of all time (red, with all time meaning since 31 December 2013). A value counts as confirmed when it has been registered within the minute by two separate detection loop pairs that were no further than 5 kilometres apart.
In case you were wondering, the Netherlands does have a speed limit which varies depending on which stretch of motorway you are on, but the default (and highest limit) is 130 kilometres per hour. The values you see on bestwelsnel.nl all indicate speeding. The fine for going 39 kph over the speed limit on a motorway is 400 euro, if you go faster than that and get caught you have to appear before a judge.
This is an example of open data slowly getting more traction in the Netherlands—except in some cases it seems.
(Illustration: partial screen capture of bestwelsnel.nl)