This is the bicycle symbol for use on roadway/highway signage in the U.S. The image was originally extracted from a pdf document and converted to svg in Adobe Illustrator CS2. A green background has been added to this particular image to get around Internet Explorer's deficiencies in transparency rendering.
FHWA 2004 Standard Highway Signs Manual - Appendix: http://mutcd.fhwa.dot.gov/ser-shs_millennium_eng.htm
Original image created by employee of U.S. Government