If anybody thought this wasn't a joke, perhaps these sections will convince you otherwise:
Originally Posted by study
Winter versus summer
There was a statistically significant difference between times in the first (winter) and second (summer) halves of the trial. My summer clothing was relatively tight fitting. Looser shell winter clothing may increase drag by as much as 30%. Another factor that might increase journey time in winter is fear of falling off. When the road is wet or there is the possibility of ice, then the cyclist is more cautious. Winter is also associated with higher winds, and, as all cyclists know, the wind is always against you!
Traffic
Regardless of whether the bike is carbon or steel, you still have to stop at junctions and red lights.