In settings with space travel we often see stories that rely on ships encountering each other, such as space piracy (which means you need to know where to wait in ambush), or distress signals that actually get answered by passing ships. Now on earth the idea of shipping lanes make sense because of currents and winds (not all paths across the ocean are equivalent), and we have similar factors with air traffic. But even if we didn't have these factors, in the grand scheme of things Earth's navigable airspace and waterways are pretty small.
Space, on the other hand, is big. When you're talking about traveling between planets (to say nothing of systems that are light-years apart), there are lots of ways to get there and, asteroid fields aside, vast swaths of big open space.
So is it realistic that common routes -- "shipping lanes", if you will -- would develop? If so, what factors would govern their placement? If my story depends on unplanned encounters between spaceships, what do I need to take into account to make that realistic?
As far as travel technology is concerned (e.g. FTL?), I haven't thought through the implementation yet. I am not thinking of fixtures like wormholes or B5's hyperspace lanes, where you have to follow a particular path, but if "shipping lanes" make sense for other reasons, I can imagine developing something like hyperspace lanes as a response. In other words, I'd like to do the "traffic study" before deciding how the ships work, and let the needs/patterns govern the implementation instead of the other way around.