Police have hit out at "dangerous and irresponsible" motorcyclists following a spate of deaths and serious injuries to riders on the roads in Sussex.
In the last three weeks, four people died and two others were so badly injured they are "unlikely to survive".
"Research shows that nine out of 10 motorcycling fatalities are on 'A' roads and riders themselves are the cause," said Insp Mark Armstrong.
"The latest collisions support these findings," he added.
The motorcycilsts died in accidents at the weekend.
On Saturday evening Adam Sutton, 30, from Lewes, East Sussex, died when his Yamaha YZF left the road, mounted a pavement and metal garden fence and ended up in the garden of a house in Avis Road, Newhaven.
On Sunday, a 36-year-old man from West Sussex, riding a Suzuki, died at the scene of an accident on Racecourse Road, Goodwood.
Sussex Police said the majority of fatal collisions involved single motorcycles, where the rider had lost control of his machine.
A spokesman said motorcyclists failed to respect the road, ignoring road signs and markings.
He said it was coupled with thrill-seeking behaviour such as excessive speed, taking risks by overtaking in the face of oncoming traffic, inexperience and riding beyond the capabilities of themselves or their machines.
"Motorcyclists will tell you that the main cause of their crashes is car drivers not looking properly and not seeing them," said Insp Armstrong.
"This may be true in urban areas where lower speeds make fatalities rare, and in some very few cases on the open road, but it is largely a myth.
"Unless motorcyclists face up to their own responsibility for these deaths, more will follow.
"There is still a hard core of riders, a fair number of them old enough to know better, predominantly using high powered sports bikes to treat the roads like a race track."
The latest accidents involving serious injuries to motorcyclists happened on Friday evening.
In the first, a 39-year-old man on a Suzuki GSXF from Worthing was in collision with a Porsche in Hove.
In the second, a 29-year-old man from Southwick was injured in a collision involving a Toyota car in Portslade.