1. THE 1977 JAPANESE GRAND PRIX
Racing aficionados have a special place in their hearts for the Canadian legend Gilles Villeneuve. His son, the Formula 1 champion Jacques Villeneuve, is more familiar to most people these days, but Gilles was one of the most thrilling drivers of his day, known for his daredevil attitude to the sport. As the man himself once said, "The simplest way to find the limit is to go quicker and quicker until you go over it." Sadly, he was involved in one of the most tragic collisions ever to befall a Grand Prix.
While trying to overtake a rival during the Japanese Grand Prix, their cars collided, sending Villeneuve's Ferrari cartwheeling into the air and over a barrier - right where spectators happened to be standing. A race marshal and a photographer were killed, but Villeneuve himself miraculously walked away. But fate had Villeneuve in its sights, and he would himself perish after a very similar collision in 1982 flung him fatally from his car. .
2. THE 1977 SOUTH AFRICAN GRAND PRIX
One of the most unlikely, gruesome accidents in sporting history took place during the 1977 South African Grand Prix. It started off innocuously enough. Italian driver Renzo Zorzi realised his engine was failing, so he made the decision to pull over on the side of the track. The engine promptly erupted into flames - a startling spectacle, yes, but nothing life threatening, as Zorzi had safely climbed out of his seat and was standing well away from the stricken vehicle.
But then, two marshals made the disastrous decision to come to Zorzi's aid by rushing across the track. The trouble was, there was a dip in the track, meaning they couldn't see any cars approaching - and the drivers couldn't see them. One marshal made it across. The other, a lad of just 19, was hit side-on by a sudden car. He was killed by the impact, while the fire extinguisher he'd been holding was thrown right at the head of the driver who hit him: Welshman Tom Pryce. The extinguisher smashed into Pryce's helmet, instantly killing him. Pryce's car would grimly drive on, the driver dead at the wheel, while crowds watched in horror.
3. THE 1978 ITALIAN GRAND PRIX
Some crashes are far worse than they initially appear. This was the case at Monza race track in 1978, when what seemed to be a non-fatal accident took a much darker turn. It was all down to the race starter being a bit too enthusiastic, and signalling the green light when the cars hadn't finished lining up properly. What ensued was chaos, as the cars lurched forwards at speed, bunching messily together with hardly any room not to have a collision.
Several drivers - including legendary British driver James Hunt - crashed and banged into each other, and one driver, "Super Swede" Ronnie Peterson, smashed into a barrier. His car went up in flames, and other drivers managed to pull Peterson out before he was too badly burnt. His legs had been badly damaged, but his condition was thought to be stable. If anything, medics were more concerned about another driver who'd been hit on the head with a wheel. But it was Peterson who unexpectedly succumbed to complications in hospital, dying the next day.
4. THE 1986 RALLY DE PORTUGAL
The 1980s saw the rise of the now-notorious (and legendary) Group B rally cars. These were designed to be both incredibly light and ferociously powerful - a combination which made them thrilling to watch, but upped the danger factor considerably. Things came to a head in 1986 during the Rally de Portugal - a race that was already infamous for allowing fans to stand perilously close to the road. Some drivers were actively worried about racing, due to the crowds pushing in just centimetres from their whooshing cars.
People's fears were realised in 1986 when driver Joaquim Santos lost traction. His car swerved off the road and ploughed straight into the crammed crowd, killing three spectators instantly, with a fourth dying later. Dozens were injured, and the terrible incident was one of the nails in the coffin of the Group B era.
Watch Rallying - The Killer Years on UKTV play.
5. THE 1955 24 HOURS OF LE MANS
One of the worst disasters, not just in motor sports but in all sports, happened out of nowhere during the epic 24 Hours of Le Mans in 1955. It came down to a fatal move by the dashing, charismatic Mike Hawthorn, who was driving for Jaguar and determined to beat the Mercedes team. Making a sudden pit-stop, his lurch to the side of the track forced another driver, Lance Macklin, to swerve to avoid smashing into Hawthorn.
That put Macklin dead ahead of Frenchman Pierre Levegh, whose car rode right up Macklin's car and flew into the air like a missile. Levegh was killed when he was thrown from the car and the vehicle itself fell apart, sending shrapnel spinning into the densely packed crowd. At least 83 people died in seconds, with many spectators decapitated where they stood.
Watch Deadliest Crash: Disaster at Le Mans on UKTV play.
Watch Mike Hawthorn: On The Limit on UKTV play.