Was the road dry or wet? Stock tires? I've gone down twice as well - streetcar tracks and being cut off being one reasons, another time it was a bad driver, wet road, and a VERY badly timed gust of wind. But I've almost gone down once or twice when my tires lost grip... the stock tomos tires (The "slick" so called performance tires" don't seem to grip all that well in anything less than ideal pavement conditions. (could just be my perception of things however)