S-50d
Lanes reserved for traffic by posted speed
Indicates that the lane bearing the minimum speed sign may be used only by vehicles traveling at or above the indicated speed, although when circumstances allow they should use the right-hand lane. The end of the minimum-speed requirement is marked by sign S-52 or R-506.
Category: Lane signs
Source: General Traffic Regulations (RD 1428/2003), Annex I; designs per the official sign catalog (RD 465/2025)