The shortest motorway in Pakistan is the M-8 Motorway, specifically the section near Gwadar.
While the total planned length of the M-8 is substantial, the operative section nearest to Gwadar is currently the shortest stretch considered functional. The reference specifically mentions "Gwadar's Shortest route" which indicates a functional section of the M-8 serving the Gwadar area and being the shortest operative motorway section.
It is important to note that the length may change as construction progresses on other motorways or sections of the M-8 become operational. However, based on the information available currently, the operating section of the M-8 near Gwadar represents the shortest functional motorway stretch in Pakistan.