Two men were arrested on the A1(M) near Stevenage after they were seen driving a van in suspicious circumstances in Buntingford.
Police are warning of long delays on the A1(M) all the way back to Hatfield following a crash near Welwyn.
A man in his 80s who was seriously injured in a crash on an A1(M) slip road at Letchworth Gate has tragically died in hospital - and police have today reappealed for witnesses.
Beds, Cambs and Herts Road Policing Unit are targeting motorists who pose the greatest risk on the roads.
Officers investigating yesterday's fatal crash near Hitchin have now appealed for witnesses, as they work to trace four people who left the scene before police arrived.