Ms Glare, 39, who was driving, and her husband, 41, died instantly.
Their 18-year-old daughter was taken to Ballarat Base Hospital to be treated for cuts to her face.
Bacchus Marsh police Sergeant Robert Pama told The Courier “black ice” was the main cause of the double fatality.
He said “treacherous conditions” had also resulted in a number of cars skidding off the Western Highway, including a car rollover in Elaine and numerous accidents in Ballan.
“[If you come across black ice] slow down, pull over and stop,” Sergeant Pama said.
“The [weather] is unpredictable and can have tragic consequences.”
He said police would investigate whether the 100-kilometre speed limit and ice warnings were adequate in the area, given the crash and prevalence of black ice.
The Victorian Speedway Council posted a Facebook tribute expressing sorrow felt by the “speedway family” at news of the couple’s passing.
“The VSC would like to send condolences to the Glare family upon hearing the tragic news in regards to the passing of Michael & Jo Glare from the Swan Hill Speedway Club,” it said.
“All our thoughts condolences & prayers go out to the kids & we will all miss Michael & Jo.”
Nephew Rhys Smith posted: “You were more than just my uncle, you were my bro. I love you uncle Michael TheBomb Glare and aunty Jo Glare.”
Others expressed shock at the sudden death of a couple who had devoted their lives to their children, families and others.
Later on Saturday, a woman in her 30s died in a head-on collision at Bruarong in the state’s north east.
Police say the woman lost control of her Toyota sedan and crashed into a 4WD on the Myrtleford-Yackandandah Road about 3.10pm.
Three men in the 4WD, two men in their 20s and a man in his 50s, remain in hospital.
The deaths bring the state’s road toll to 145, 22 more than this time last year.