The dangers of street circuits was further exposed at the 1975 Spanish Grand Prix held on the twisty, tree-lined Montjuich circuit in Barcelona. The racing drivers found that the circuit's safety barriers had been shoddily installed and threatened to strike if the barriers were not brought up to standard. Under pressure from race organizers, the race was started only to be stopped after 29 laps when a car plowed into the crowd, killing four spectators.