A silhouette of the left side of a semi truck consisting of a two-axle tractor and a two-axle trailer, used as a symbol on the Weight Limit symbol sign (R12-5) defined in 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>.
Federal Highway Administration
<cite class="book" style="font-style:normal">"<a rel="nofollow" class="external text" href="https://mutcd.fhwa.dot.gov/SHSe/Appendix.pdf#page=5%7Ctitle=Standard">Highway Signs and Markings Appendix</a>"      (PDF), Federal Highway Administration  <small></small></cite>