Final answer:
When a bicyclist occupies too much space to safely share the lane, motorists should slow down, wait for a safe opportunity to pass, and maintain a legal passing distance. From a bicyclist's reference frame, a stationary observer appears to move in the opposite direction of the bicyclist's motion.
Step-by-step explanation:
The proper procedure for a motorist when a bicyclist is occupying too much space for you to share the lane safely is to slow down and observe the situation. You must wait until it is safe to pass the bicyclist, which typically means you need enough clear space in the adjacent lane to move over and not come too close to the cyclist. Depending on your location, traffic laws usually specify a minimum passing distance from a bicyclist, often around 3 feet (1 meter). It is essential to check your mirrors, signal your intention to change lanes, and pass the bicyclist safely and legally. Once you're past the bicyclist, ensure you're clear of them before merging back into the lane.
If you're standing on a sidewalk and see a bicyclist passing by to your right, in the reference frame of the bicyclist, you would appear to be moving to the left. This is due to the principle of relative motion; in the cyclist's frame of reference, they are stationary, and everything else is moving relative to them.