Overstock.com employees rode their bikes to work Wednesday as part of Utah's Clear the Air Challenge, in which Utahns take alternative transportation to avoid driving vehicles in summer when air quality is at its worst. There are currently 25 employees who have signed up to participate in the biking challenge. Fourteen of the participating employees are based in Overstock.com’s corporate headquarters in Cottonwood Heights and rode Wednesday. Eleven are based at Overstock’s warehouse in west Salt Lake City and will be riding on July 30.