Original: As of May 2008, Voyager 1 was traveling at a speed of 17.1 kilometers per second relative to the sun (3.6 AU per year or 38,400 miles per hour or 61 600 km/h), 10% faster than Voyager 2.
Simplified: As of November 2005, the spacecraft was travelling at a speed of 17.2 kilometers per second relative to the sun (3.6 AU per year or 38,400 miles per hour), 10% faster than Voyager 2.