The traffic ticket contains an actual notice to you of a pending court date at which you must appear. By signing the ticket, you are providing an acknowledgment of receipt of the "notice to appear." Since the officer is charging you with a violation of law, he could take you into custody. By signing the traffic ticket, you avoid being taken into custody at that time, and are "released on your own recognizance" pending the court date. It is better to sign the traffic ticket and go about your business pending the court date. By signing the traffic ticket, you remain free and retain the right to show up at the hearing to contest the issuance of the citation or summons.
A person is free to refuse to sign the traffic ticket; however, the police officer is free to place him/her under arrest and take him/her into custody.