When is it permitted to drive on the left side of the road?

Driving on the left side of the road is permitted primarily when passing another vehicle or under specific circumstances. This rule is in place to ensure that drivers can safely overtake slower-moving vehicles without obstructing oncoming traffic. It allows for a clearer pathway when road conditions permit and should be executed with caution.

In addition to passing, there are other scenarios, such as when the road is marked for two-way traffic and you're avoiding an obstruction, or in some cases during certain road construction situations. The ability to move left is contingent on the situation being safe and legal, which is reflected in the rules of the road.

The other options do not accurately represent the guidelines for driving on the left. For example, heavy traffic does not inherently justify driving on the left unless passing, which can lead to unsafe maneuvers. Driving on the left solely at night is not a permissible condition as daylight does not change the traffic rules. Lastly, while traffic signs can direct when to use certain lanes, they do not universally authorize left-side driving without the context of passing or specific road conditions.