There is no road to Wengen. You arrive by train. From Interlaken Ost, take the Berner Oberland-Bahn (BOB) to Lauterbrunnen — about 20 minutes. Change at Lauterbrunnen for the Wengernalp-Bahn, the cog railway that climbs 400 metres up the cliff to Wengen in another 15 minutes.
From Zurich Airport the total journey time is about three hours via Bern or Lucerne and Interlaken — entirely on the Swiss rail network, all included on the Swiss Travel Pass and most rail passes. Cars must be left in the multistorey garage at Lauterbrunnen station (paid).