Preview data in the Map Service of Helsinki: https://kartta.hel.fi/link/9YWffL
Data is a collection of calculations made about traffic volumes and estimations of traffic volumes. The data contains volumes per vehicle (passanger car, van, truck, lorry, bus, motorbike, tram) per road. It also contains overall traffic rate (all vehicles combined) per year (KAVL for short) and per autumn (SKAVL for short). In addition, it includes information about percentage of heavy traffic of all traffic. Data is updated once a year.
Note that values in reference year (laskentavuosi) vary a lot. Values come from different sources: automatic counters and hand-made calculations either with regular intervals or with samples. If value in laskentavuosi is 9999, volume is estimated instead of calculated.
The data does not cover all streets of Helsinki.
The address of the WFS is: https://kartta.hel.fi/ws/geoserver/avoindata/wfs
The address of the WMS is: https://kartta.hel.fi/ws/geoserver/avoindata/wms
Data can be found in layer: Ajoneuvoliikenne_liikennemaarat_viiva
Coordinate system: maintained in ETRS-GK25 (EPSG:3879), can be projected to other systems (see Get Capabilities for supported coordinate systems)