Originally Posted by
Eyes Roll
This ^^^, first and foremost. Ride the bike at a slow or controlled pace, ensuring that you always retain control over your riding speed, which affords not only you but also other road users ample time to react and respond. Most accidents, even collisions between cars, occur as a result of poor judgment regarding the speed at which individuals are traveling. Sure, I like to ride fast, but I also keep in mind the need to slow down or ride at a controlled pace, based on the road conditions at that time.
While riding at a reasonable and prudent speed is generally wise advice (and someday I might just heed that advice on a steep descent), keep in mind that a motor vehicle door can go from fully closed to fully open in about half a second. A reasonably alert road user under normal conditions can get the perception part of the perception-reaction formula down to about 0.7 seconds (although for most road users it's typically well over one second, especially when distracted), but what that means is that if the door opens within less than one second's travel time (within 20 feet or so, or a long car length), your brain is still processing the perception part and probably hasn't quite gotten to the reaction part when impact occurs.
Hence the recommendation to avoid the area of door sweep in the first place.
It is true that under intense concentration and practice one can reduce perception-reaction responses to small fractions of a second (drag racers, quick-draw shooters, etc.), but this requires a level of focus on specific stimuli that might be very risky to employ in a busy traffic environment. And it's also rather fatiguing to maintain such a focus, and even experts can only do so for a limited time.