Final answer:
A good practice when two or more roads join and there is no signal or regulatory device is to slow down and yield to other vehicles.
Step-by-step explanation:
When two or more roads join and there is no signal or regulatory device, a good practice is to slow down and yield to other vehicles. This allows for safe and efficient traffic flow. By slowing down and yielding, drivers can ensure that all vehicles can merge and move through the intersection smoothly.