By Ella Christoph Taxis honk and confused minivans hover midintersection. Bikes slide through the streets dodging doors and inflexible drivers. The crowd at the corner builds as commuters come to a halt&mdash;&ldquo;Don&rsquo;t Walk&rdquo;&mdash;purses and briefcases still swinging. They are sprinters, waiting for the race to start up yet again, and their toes grip the edge [...]