Deceleration lane

When driving on a motorway, you signal approximately 300 meters before the exit lane to indicate to drivers behind you that you intend to leave the motorway.
When driving on an autoweg, you signal approximately 200 meters before the exit lane to indicate to drivers behind you that you intend to leave the autoweg.
You are permitted to reduce speed as soon as you are in the deceleration lane, but not before you are in the deceleration lane. (This question is frequently asked at the CBR.

How to proceed in a combined acceleration/deceleration lane has already been discussed in that topic.

Article 1 of the Road Traffic Regulations (RVV).
Deceleration lane: a section of the main carriageway separated from the main carriageway by block markings and intended for drivers leaving the main carriageway.