Drivers who don't heed the warning could face a hefty fine. Police can issue tickets for twice the normal amount if drivers are caught speeding near a construction zone.
Quebec provincial police have teamed up with Transport Quebec for an initiative, dubbed Operation Orange, that will see more police patrolling in areas with road construction.
Frédéric Leclerc, a road worker, said cars sometimes whiz past him at 140 km/h.
"It's one of the risks of this job," he said. "But it'd be great if people slowed down."
Last year, 13 people died in collisions near construction sites in Quebec, most of them construction workers.