Commuting between car lanes
One key factor is your handlebar width. This might seem obvious but I have a friend who recently bought a road bike with drop bars to replace a mountain bike as it has much narrower handler bars.

If you do have mountain bike handle bars I recommend putting your hands right at the edge, that way your brain will best gauge whether your bike will fit through, since your bikes width is also your width, and your brain knows you pretty well! This little trick is what cats use to judge spaces knowing their whiskers are the width of their body.