In the Sherlock Holmes mystery The Priory School, a telling piece of evidence comes from the observation and ensuing analysis of a pair of tire tracks, which Holmes assumes are made by a bicycle.  The critical part of the analysis is an argument by Holmes that one can determine the direction that a bicycle was traveling from the tire tracks.  Consider the following variation in the Holmes mystery. 
Imagine that Holmes and Watson discover a single tire track instead of a pair of tire tracks while walking down a path at the Priory School.  Could Holmes and Watson determine the direction the cyclist was heading (assuming of course the tire track was made by a cyclist)? 
It seems natural to suspect that Watson would come to the obvious conclusion that the tire track was created by a unicycle, and thus the direction can not be determined from the track.  However, one could imagine that Holmes would chide Watson and draw on his famous question to Watson,  "How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?", to consider the question could a bicycle have created this single tire track. 

Our goal in these pages is to examine this possibility.  [The answer is of course yes, a bicycle can create a unicycle track.] 

Could a bicycle have created this single tire track?