Sign R9-23bL “Two-Stage Bicycle Turn Box” from FHWA Interim Approval 20, intended to be added to the next revision of the <i><a href="https://en.wikipedia.org/wiki/Manual_on_Uniform_Traffic_Control_Devices" class="extiw" title="w:Manual on Uniform Traffic Control Devices">Manual on Uniform Traffic Control Devices</a></i>, with text converted to paths for display.
Federal Highway Administration
<a rel="nofollow" class="external text" href="https://mutcd.fhwa.dot.gov/resources/interim_approval/ia20/index.htm">Interim Approval for Optional Use of Two-Stage Bicycle Turn Boxes (IA-20)</a><a rel="nofollow" class="external autonumber" href="https://mutcd.fhwa.dot.gov/resources/interim_approval/ia20/ia20_attachments.pdf#page=7">[1]</a>