Group B regulations required only 200 road-car homologation units, far fewer than previous classes. This low threshold enabled manufacturers to design purpose-built machines with exotic materials, mid-engine layouts, and all-wheel drive that bore little resemblance to their nominal road-car counterparts. By 1986, the leading Group B cars — the Peugeot 205 T16 Evolution 2, Audi Sport Quattro S1, and Lancia Delta S4 — were producing in excess of 500 horsepower in some cases. Cars had evolved at a pace that regulations never anticipated controlling.
The format of WRC events amplified the danger. Stages ran on public roads temporarily closed for the event, with spectators lining the route, often standing on the road surface itself. Crowd control was left largely to organizers of individual events, with no consistent standards across the calendar. Michèle Mouton later described having to mentally treat spectators as trees in order to drive competitively at speed.
The 1986 season opened with two tragedies in quick succession. At the Rally de Portugal in March, Portuguese driver Joaquim Santos crested a rise on the opening stage near Sintra, turned to avoid spectators on the road, and lost control of his Ford RS200, which slid into a crowd. Three people were killed and thirty-one were injured. The top teams immediately withdrew from the event. Several drivers issued a statement declaring it "impossible to guarantee the safety of the spectators," though they attributed the accident not to the cars themselves but to the presence of spectators on the road surface.
Two months later, at the Tour de Corse in May, Henri Toivonen was the championship favorite and leading the rally comfortably. Seven kilometres into the 18th stage, his Lancia Delta S4 left the road on an unguarded bend and plunged down a steep wooded hillside. The car landed inverted, rupturing its fuel tanks. A combination of Kevlar bodywork, a red-hot turbocharger, and leaking fuel caused a fire that consumed the car in the undergrowth. Toivonen and his co-driver Sergio Cresto died at the scene. No witnesses observed the accident, and the exact cause was never determined.
These deaths followed the 1985 fatality of Lancia driver Attilio Bettega during that year's Tour de Corse, and combined with the televised crash of Formula One driver Marc Surer at that year's Hessen Rally — in another RS200, which killed co-driver Michel Wyder — the cumulative toll forced a regulatory response.
The FIA acted immediately. Immediately following the Toivonen and Cresto deaths, the governing body announced that Group B cars would be prohibited from WRC competition from 1987 onward. Group A was designated the new top class, with engine limits of 2,000 cc and a power ceiling of approximately 300 horsepower. The FIA also abandoned its planned Group S regulations, which would have allowed a more controlled evolution of ultra-high-performance rally cars with a minimum homologation requirement of only ten units.
Audi announced it would quit rallying entirely, citing the FIA's failure to address spectator safety directly. The season concluded with its own controversy: Peugeot was disqualified from the Rallye Sanremo by Italian scrutineers over bodywork legality, handing the manufacturers' lead to Lancia's Markku Alén. The FIA subsequently annulled the Sanremo result eleven days after the United States round, transferring the championship to Peugeot's Juha Kankkunen — who became the last Group B world rally champion.
The Group B era is remembered simultaneously as rallying's golden age and its most dangerous chapter. The cars represented an engineering peak — lightweight spaceframe chassis, aerodynamic bodywork, sophisticated four-wheel-drive systems, and turbocharged engines — that has not been matched within their category even decades later. Critics of the ban argued that the cars themselves were not the primary danger; crowd control failures and inadequate stage design were the systemic problems. Proponents of the ban pointed to the exponential pace of performance development with no regulatory ceiling in sight.
Former Group B cars found new homes in European rallycross events from 1987 through 1992, and Peugeot adapted the 205 T16 for the Dakar Rally, where Ari Vatanen won in 1987, 1989, and 1990. Audi deployed Group B technology in American racing series. The Group S concept was indirectly revived in 1997 through the World Rally Car specification, which brought back purpose-built rally machinery with more controlled parameters.
The Group B ban fundamentally reshaped rallying's identity. The switch to Group A made the sport more accessible and commercially viable, connecting WRC machinery more closely to production models, but the era of unchecked engineering ambition it ended has never returned.