We can actually see what will happen if we look south. Speed limits on US highways have been increasing over the last 10 years and this is accompanied by increased motor vehicle fatalities.
per IIHS:
“Raising speed limits leads to more deaths.”
.
British Columbia reduced some speed limits in 2018 -
Province rolls back speed limits on 570 km of highway | BC Gov News
The British Columbia government is lowering speed limits on 15 sections of highway in the province to keep people safer and reduce the chance of speed-related collisions.
news.gov.bc.ca