Thanks! That MV police blog post says the traffic officer stopped the car to &quot;educate the operators about impeding traffic per 22400(a) of the California Vehicle Code.&quot;<p>That section of the vehicle code says, emphasis added:
&quot;No person shall drive upon a highway at such a slow speed as to impede or block the normal and reasonable movement of traffic, unless the reduced speed is necessary for safe operation, because of a grade, <i>or in compliance with law.</i>&quot; <a href="https:&#x2F;&#x2F;www.dmv.ca.gov&#x2F;portal&#x2F;dmv&#x2F;detail&#x2F;pubs&#x2F;vctop&#x2F;vc&#x2F;d11&#x2F;c7&#x2F;a2&#x2F;22400" rel="nofollow">https:&#x2F;&#x2F;www.dmv.ca.gov&#x2F;portal&#x2F;dmv&#x2F;detail&#x2F;pubs&#x2F;vctop&#x2F;vc&#x2F;d11&#x2F;c...</a><p>If Google&#x27;s self-driving cars are limited by law to 25mph, and the car was not exceeding 25mph, then it was &quot;in compliance with the law&quot; and 22400(a) doesn&#x27;t apply. It would be allowed to impede or block traffic, even if we human drivers would really prefer it to be going 45mph.