The literal meaning of "the rule of the road" (often referred to in its plural "the rules of the road") entails all of the precautionary methods one must put in place to ensure that one is driving defensively rather than offensively. It is the set of mandates imposed upon operators of any motorized vehicle meant to safeguard the safety and security of everyone on the road.
From a figurative point of view, the "rules of the road" hold the significance of being a higher order paradigm which can be applied to anything. For instance, should we apply "rules of the road" to our everyday life, with or without vehicles, a lot of problems can be avoided. The truth is, however, that we do put "rules of the road" into our everyday activities: we have stop lights in traffic that tell us where to proceed to drive safely. There are signs with information in major places asking us not to do certain things: not throw trash on the ground, to please recyle plastics, to please pick up after our pets if walking outside, etc.
Other rules that benefit everyone include rules for safety in pools, in public parks, for public facilities (outside bathrooms), and even during events and activities which warn us from not bringing glass containers, or weapons, or any other object which may potentially harm others when not used properly.
The reason why the name "rules of the road" has "stuck" is because humans, particularly adults, DO need to be re-directed consistently in order to, finally, change a behavior. Schools and teachers do this when we are children. However, we assume that being adults makes us all mature and knowledgeable. That is absolutely not the case, sadly but true. Hence, the regulations placed in key places which beg for adults to follow the proper ways of behavior, etiquette, and even ethical behavior, become "the rules of the road" to life, rather than just for the purpose of driving properly.
The rule of the road is to prevent cars from colliding with each other as they move along in traffic.
Figuratively, it could mean taking the taken path, following the rules laid down by previous people on how to move down that path.
The rule[s] of the road means, in literal terms, the safety regulations one must take when driving on a road, such as stopping at stop signs and red lights, signaling, paying attention to traffic lights, etc. However, the saying itself can be applied to other things as well. I always understood it as if you follow "the rules of the road" that you are taking the safe route and doing what is right/expected. Basically, it is following regulations (in any situation) that will keep you on track and safe.
The literal meaning of rule of the road is the regulation of he direction of which 2 vehicles should move to avoid collision. The figurative meaning of rule of the road is something you should know to help you in what you're doing.
The rule of the road can be defined as," a customary practice (as driving always on a particular side of the road or yielding the right of way) developed in the interest of safety and often subsequently reinforced by law; especially : any of the rules make up a code governing ships in matters relating to mutual safety."
When you are just talking about driving, the rule of the road can be summarized as the laws you must follow while operating and driving a vehicle. For example a rule of the road (in the U.S.) is to always drive on the right side of the road. This is to try and prevent vehicles from having collisions. Different states have different driving laws which are important to know if you are traveling. Some states have a "rule of the road" where you cannot talk or text on a cellphone and must only talk through a hands free device. Other states have yet to put this law into place.
The rule of the road is simply the laws you must follow when you are driving.