Quote:SUNNYVALE, Calif. (AP) - A tech-savvy prankster has been tampering with traffic lights in this Silicon Valley town, turning them off and rejigging wires so the lights flash red in all directions.

The prankster also has surreptitiously turned traffic lights to face the wrong way, mixed up the audible crosswalk signals that help guide the blind and thrown off the timing of lights to delay drivers.

City officials have launched a publicity campaign in hopes of thwarting the unknown crafty engineer, who has evaded the law for months.

The trickster has been performing antics for three months and has used a key to open control boxes and reprogram the lights. Most audaciously, he or she recently used a cherry-picker truck to turn an overhead signal across a busy intersection - but no residents or city officials reported any unusual activity.

No one has been hurt because of the pranks. Nonetheless, after ruling out insiders who work for the traffic division, Sunnyvale officials are asking residents to put down their cell phones and handheld computers and look for anyone tinkering with lights.