Mr Hannigan was hit on the southbound carriageway at about 18 20 BST on Saturday, and police later appealed for witnesses.
The incident happened on the northbound carriageway at about 05:10, between J5 at the Raith interchange near Hamilton, and the M73 slip road at J4.
BBC South East special correspondent Colin Campbell and his producer were driving along the main motorway into Calais on Wednesday when they were brought to a halt by a tree that had been dragged on to the dual carriageway at about 04:00 local time by the people-traffickers.
The southbound carriageway will be opened about 45 minutes later.
The southbound carriageway eventually reopened at about 17 00 BST.
Emergency crews were called to the two-vehicle crash on the northbound carriageway, near Northallerton, at about 11 50 BST.
The first man died when his car hit a stationary lorry on the A8 dual carriageway near Ballynure at about 07:50 GMT on Saturday.
Admittedly, this sends everything in the back flying because there are no cubbyholes or even magazine holders in the back of the seats, but on motorways you don't have to worry about joining the carriageway.
A colonnaded street, in Roman times more than 88 feet (27 metres) in width (about one-third carriageway and one-third for each sidewalk), ran the city's length.
Tayside Fire and Rescue Service said a van driver had to be rescued after his vehicle got stuck in water covering a stretch of about 100m of carriageway.
