During 1937 the Italian Ministry of War issued specifications for a new armoured car (autoblindomitragliatrice), to fulfil the requirements of both colonial police long range patrols and army reconnaissance units for the new armoured formations. In May 1939 the Fiat-SPA and Ansaldo-Fossati consortium unveiled its armoured car proposal, named Abm 1, at the inauguration of the new Fiat Mirafiori plant near Turin; two prototypes had been built, one outfitted for military and one for police use.
After trials by the Army, in May 1940 the armoured car was standardised, adopted with the official designation Autoblinda 40, and a first batch of 176 vehicles ordered. At the request of the Army the prototype had undergone numerous changes before it was adopted: redesigned front hull, recessed headlamps under armoured covers, improved ventilation, new cast spoked wheels, and flat, shortened mudguards. The first AB 40s were delivered in March 1941.
The Autoblinda 40 was built in small numbers in 1940. Armament consisted of two 8 mm machine guns in a turret. During production a need for heavier armament was envisioned and so the AB 40 was redesigned as the AB 41 which was the same vehicle except for a new turret with a 20 mm autocannon. Most of the 24 AB 40s that had been built were then converted to AB 41s.
The Autoblinda 41 (named after its first year of production, 1941) was a further development of the machine gun armed AB 40. Made with an all-riveted construction, the AB 41 had four-wheel drive and a four wheel steering system that proved troublesome. The spare wheels fitted to its sides were free to rotate, thus helping the vehicle over rough terrain and allowing it to drive over higher obstacles. It could also be fitted with wheels that would allow it to run on railway tracks and some were modified further to better serve in this role, with the addition of sand boxes and rail guards to deflect objects from the rails. This version was designated AB 41 Ferroviaria.
It had six forward gears and four reverse gears, with a driving position at the front and one in the rear, so two crew members were drivers. Overall the AB 40/41 family was well thought out, with a top speed of over 70 km/h (45 mph), good armour (15 mm on the front plates) and good road and cross-country performance, but there were some examples of poor detail design like difficult access to the powerplant, an unprotected fuel tank, one-man turret, exposed traverse gear and lack of an interior bulkhead separating the engine and crew compartments. Nevertheless, the AB 41 was considered a good vehicle and one of the best armoured cars of its era. Its chassis was later used as a basis for the SPA-Viberti AS.42. About 550 vehicles were built in all. The Italians planned to upgrade the AB 41 with a 47 mm anti-tank gun as the AB 43, but those plans were disrupted by the Armistice of Cassibile in September 1943.