Final answer:
Objects may extend beyond the left side of a vehicle only in compliance with local regulations, and a distance of six car-lengths from an oncoming vehicle can be considered as a rough guide for crossing a road safely.
Step-by-step explanation:
You can lawfully allow an object to extend beyond the left side of your vehicle in compliance with local regulations. When deciding to cross a road or a junction, the safe distance you must maintain from an approaching car can vary based on several factors, including the speed of the oncoming vehicle and your ability to accurately judge speeds and distances. A commonly suggested distance is waiting until the vehicle is at least six car-lengths away before considering it safe to cross, though this is just a rough estimate and the actual safe distance should always be judged in the specific context of the situation.