In Santa Clara County, the streetcar - or "light rail" - lines are marked with interlocking traffic lights. Signs along Tasman Avenue in San José are typical of the symbolic signs used to warn drivers of light-rail crossings.
It should be noted that most streetcar crossings in San Francisco are not marked. In many cases, it wouldn't be practical, because the streetcar rails usually run down the center of the street and are not otherwise separated from traffic in any way.