Lærdal has always been the main traffic artery between east and west. The first road over Filefjell came during the Middle Ages, then the public postal route over Filefjell through Lærdal in 1647. In the 1790s, the Kongevegen over Filefjell was built over Filefjell, and in the 1840s it was upgraded to the Bergen main road.
Today, from Sogndal you can take the ferry with Norled from Mannheller to Fodnes in Lærdal. From Årdal, it takes about 30 minutes by car.
From Oslo you can drive over Filefjell or Hemsedalsfjellet. Check the traffic conditions on Statens Vegvesen web page.
From Bergen, drive E39 via Voss, Flåm and Aurland.