That’s a great question! Yellow lines and speed limits however, do not have a relationship in this regard. If there are no speed signs posted on a road, regardless of the presence of yellow lines, then technically the speed limit is 50 km/hr in towns and cities (not talking about highways and freeways). In the lanes (back alleys) the speed limit is 20 km/hr unless posted.
Keep in mind the “speed limit” is the maximum allowable limit; it does not mean that you should necessarily drive 50 km/hr.
In my experience roads that do not have yellow lines are typically found in residential areas and can be narrow and/or have many potential hazards such as kids, pets, curves, blind driveways, etc., Drivers should determine appropriate speeds based on conditions, even when the legal maximum is 50 km/hr.
There are so many distractions while driving and numerous signs to read… we don’t need a 50 km/hr sign on every road and on every block to add to the distraction of driving. Hopefully, drivers will decide to drive maybe 30 km/hr or 40 km/hr when they see good reasons like children playing etc.
Drivers can fail road tests, receive warnings or tickets for driving too fast for conditions. Please be a thinking driver and not a mechanical auto-piloted robot.