Bicycle safety expert: Bicycling on the left half of the road is much more likely to lead to collisions with automobiles than is bicycling on the right. After all, in three different studies of bicycle-automobile collisions, the bicyclist was riding on the left in 15, 17, and 25 percent of the cases, respectively. Skeptic: But in places where a comparatively high percentage of bicyclists used to ride on the left, there was surprisingly little decrease in collisions between bicyclists and automobiles after bicycling on the left was made illegal. One reason the strength of the bicycle safety expert's argument cannot be evaluated is that ['the statistics it cites do not include the percentage of bicycling that took place on the left', 'bicycling on the left is singled out for criticism without consideration of other bicycling practices that are unsafe', 'no statistics are provided on the proportion of bicycle accidents that are due to bicycle-automobile collisions', 'it does not distinguish between places in which bicycling on the left is legal and places in which it is illegal']