HORSHAM Highway Patrol has appealed for witnesses after two vehicle chases at the weekend.
Senior Constable Cam Cooper said police tried to intercept a dark coloured sedan at 11pm on Friday on Lillimur-Yearinga Road near Kaniva.
"Police tried to intercept the vehicle for a routine check and when the driver failed to pull over, police pursued the vehicle for a short period," he said.
"When speeds reached in excess of 170kmh, the pursuit was terminated due to dangerous speeds."
Horsham Highway Patrol also pursed another vehicle in Horsham less than two hours later.
"At 12.40am on Saturday, police came across a white motorcycle on Remlaw Road," Sen Const Cooper said.
"Police indicated to the driver to pull over and the driver failed to stop."
Sen Const Cooper said the motorcycle turned into Hillary Street and was travelling at more than 80kmh in a built-up zone.
"Due to the driver's erratic behaviour, the pursuit was terminated," he said.
The motorcycle was last seen travelling through a laneway between Hillary and Phillip streets.
Sen Const Cooper said at one stage the motorcycle crossed to the wrong side of the road in front of an oncoming car.
He said police were looking for any witnesses who might have seen the vehicles.
He urged anyone with information to call Horsham Police Station on 5382 9200.