MELBOURNE, Aug 10 - Year 8 student Xinyu Yuan and her mother Ma Li Dai were leaving parent-teacher interviews at Lighthouse Christian College in Cranbourne East when their car was hit by an oncoming Commodore on Wednesday night. 

Both died instantly. 

Crash investigators are examining whether speed and alcohol were factors in the crash, but have been told the Commodore was seen overtaking a number of vehicles on the highway before the crash.

Acting Assistant Commissioner Tim Hansen said investigators are looking at whether a "heated discussion" at a nearby pub may have impacted the driver's state of mind.

"We all have relationship issues - that doesn't then justify us getting into our car and driving like a hoon down the road and endangering the lives of others," he told reporters on Thursday.

The 26-year-old driver, from Devon Meadows, was taken to hospital suffering serious injuries.

Crash investigators conducted skid tests outside the school gates on Thursday morning, driving a vehicle at high speed before coming to a screeching halt.

Tests were made firstly with anti-lock brakes and then without, the latter sending the car skidding further with smoke coming off the tyres.

The stretch of highway outside the school has cars roaring past at 100km/h and Lighthouse Christian College principal Jacob Mathews says he's been asking authorities to lower the speed limit near the school for years. 

"We have asked for an 80km/h zone here, there are 80km/h zones both south and north of us," Mathews told 3AW on Thursday.

Roads Minister Luke Donnellan offered his sympathy after the crash and said the section of highway will be further investigated.

VicRoads reviewed the road in 2016 and the 100km/h speed limit was found to be appropriate after the modification of a nearby intersection.

But the road authority on Thursday said it will "will look at what can be done to improve safety for drivers exiting the school's driveway" once the police investigation is complete.