rule of the road

plural rules of the road

1. Any of the requirements for how drivers, bicyclists, etc, behave and operate while using public roadways.

   To obtain a driving licence, you must pass a test to show that you understand the rules of the road.

   1 more example

   It is a rule of the road in this country that a motorist must yield to a pedestrian who is in a pedestrian crossing.

2. The regulation requiring all traffic (travelling on a road or otherwise) to keep either to the left or the right.

   The general rule of the road for steamers is precisely the same as the general rule of the pavement for foot passengers in London […]

   1869, Thornton Alexander Jenkins, The Rule of the road at sea and in inland waters, page 214

   2 more examples

   Hence in Japan the influential samurai warriors habitually kept to the left while walking or riding. Their example influenced other travellers and resulted in the modern rule of the road in Japan: keep left.

   1986, Peter Kincaid, The rule of the road: an international guide to history and practice

   The Liverpool and Manchester railway, the first steam-operated passenger railway, which opened in 1830, adopted the British rule of the road, with trains passing each other on the left.

   1986, New Scientist (volume 112, numbers 1540-1541, December 1986-January 1987)

3. (nautical) A regulation concerning safe handling of vessels on roadsteads, seaways, sea lanes, etc.
4. countablefigurativelyA basic (fundamental) and general requirement or principle for how to operate or behave in a certain context or domain (for example, an industry, an occupation, a company, an association).

   You can't fill in fraudulent information on this form if you want to keep your job at this company. That's not a suggestion, that's just a rule of the road around here.