I started my current commute location in January. I tested some different routes and found the most obvious is the shortest. There are alternate routes that can add .3 miles. The alternate routes are nice for variety and keep me off the main arterial during inclement weather.
My ride home I'm more flexible because I have more time. As the weather improves I'll increase the distance rather than shortening it.
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"I've been dropped a lot of times, but it's never been because of my bike." DXchulo