From the Association of Metropolitan Planning Organizations (AMPO):

The FHWA published a notice that the new effective dates for both PM2 and PM3 are now March 21, 2017. The official notice can be found here: PM2 and PM3 Delayed Effective Date

This notice is consistent with the memo issued on January 20, 2017 regarding the temporary postponement of the effective dates of any, and most new, regulations published that are not yet in effect. If you have any further questions you can contact Francine Shaw Whitson at francine.shaw@dot.gov