There is a Filipino word used for falling by yourself for whatever reason or factor – semplang. The term applies for those riding a bicycle or motorcycle where a person has basically no one to blame but himself/herself for falling. Of course, there will be factors like weather and road conditions. Wet, slippery roads can be very treacherous. So are roads with potholes and/or open manholes. In most cases, however, the rider’s skill more than the other so-called factors that could have affected his movement and balance.
I am not certain about the condition of the rider in the photo above. While he looked shaken up (surprised?) by the incident, it did not seem to me as if he was moving abnormally (i.e., intoxicated or disabled). Perhaps its his skill that led to this? Such could not have been the case if he had sufficient training and experience and properly licensed to ride a motorcycle. Sadly, a lot of motorcycle riders are not well trained and gain skills only from experience. Yet, there are many who ride like they are stuntmen, often risking their lives and limbs as they maneuver (weave) through traffic.