B.C. RCMP have issued a warning to motorcyclists to slow down after four ended up hospitalized within 24 hours following crashes on highways leading from the Lower Mainland. 

The Sea-to-Sky Highway between Vancouver and Whistler was shut down for several hours on Saturday after two motorcycle riders on Harley-Davidsons crashed into each other near Porteau Cove at about 12:30 p.m. PT.

Porteau Cove, B.C.Porteau Cove, B.C.

The riders, a man and a woman, were airlifted to Vancouver General Hospital with serious injuries.

In a statement, Sgt. Peter Thiessen said that the two riders had been separated and were trying to meet up.

"One of the riders was attempting to pass another vehicle to join up with the other rider and in doing so, the first rider slowed and the second rider collided into the first rider," he said.

Highway 99 was reduced to single-lane traffic in each direction for much of the afternoon as police documented and investigated the scene.

A 44-year-old New Westminster man who was riding his motorcycle on Highway 99 near Britannia Beach around the same time had difficulty stopping as traffic in front of him slowed down. He didn't hit any other vehicles, but ended up off the road with minor injuries.

On Friday, a 44-year-old man from Chilliwack was airlifted to Royal Columbian Hospital after losing control of his motorcycle while he was travelling with a group of motorcyclists westbound on Highway 1, at McCallum Road in Abbotsford.

He was unable to stop when traffic suddenly slowed down, and ended up sliding down the highway.