MUTCD R4-21L · Regulatory signs
This lane is designated for left turns only
What it means
Indicates that this lane is designated for left turns only.
What to do about it
It is a regulatory sign: it states a law you must obey, not a suggestion. Ignoring it is a citable violation. (MUTCD R4-21L.)
Practice this on the real test format
Signs are the part of the DMV written test people fail on, because reading them is a skill rather than a fact to memorize. Aprobify drills all 1034 of them, and tells you why each answer is what it is.
Get the appSign designations follow the MUTCD and the California MUTCD published by Caltrans; meanings are checked against the California Driver's Handbook (DL 600, rev. 6/2025). Edited by Fernando Aguilera. Aprobify is not affiliated with the California DMV.
Signs in the same family
These sit next to it in the regulatory signs series — the ones most easily mixed up with it.
- R4-18 Prohibits passing other vehicles using the shoulder
- R4-19 Required clearance distance when passing bicycles
- R4-20L Requires all traffic to turn left at this location
- R4-20R Requires all traffic to turn right at this location
- R4-21R This lane is designated for right turns only
- R5-1 Prohibits entry to all vehicles
