A gang made off with €5m in a similar heist on the same stretch of highway in 2014.
Thieves burned vehicles and scattered nails on an Italian highway in a failed effort to rob a convoy of cash-carrying armoured vehicles.
At least a dozen cars and trucks were set ablaze in either direction on the highway to Bologna from Milan, and two vehicles were driven towards the convoy in an effort to get it to stop.
One of the vehicles driven by the gang then rammed the truck that was believed to be carrying the cash.
The heist was foiled after the driver pulled into a rest area and managed to get a police patrol car to intervene.
Police believe the gang was between 10 and 20-strong, and are appealing for witnesses.
A similar heist in 2014 saw thieves make off with €5m in cash on the same stretch of highway.