The main issue on divided freeways is that in most cases where the posted speed limit is 100, the design speed of the road is closer to 120 and thus, people will drive the speed it feels safe to do so. With this in mind my preferred solutions would be:
-Where the design speed allows for 400 series highways, set speed limit to 120 and start enforcing at 125. Fuctionally, there is no difference between this speed and what is practiced today.
-Double the existing fines for speeding for existing drivers
-Where potential road hazards exist such as weaving and bends in the highway, post signs indicating "Drive to Conditions"
-Narrow the lane width in areas before such hazards to encourage slower speeds
-Increase the fine where a driver travels well below the speed of traffic flow without hazards or additional lighting or signage; revise wording to indicate a 30km/h difference. If you are unable to safely drive the speed limit on the freeway for any reason (age, condition of vehicle, confidence, ect.), then you should not be driving on the freeway.
-Add a fine to penalize drivers who travel over 20km/h over the flow of traffic. This means that if the speed limit is 120km/h, the traffic is flowing at 80km/h, and you are still attempting to travel at 110km/h, you are subject to a fine and charge. Make this fine the equivalent of driving 20km/h over the posted speed limit and treat it as the equivalent of speeding.
Where traffic volumes are heavy, the flow of the road will slow down anyways. *Most* Drivers have the capability to self-regulate their speed to keep a safe following distance under these conditions.