They don't talk about shields or other measures to limit light pollution sideways and upwards, but there is at least a mention of effects on Lick Observatory an

They don't talk about shields or other measures to limit light pollution sideways and upwards, but there is at least a mention of effects on Lick Observatory and other dark-sky fans. I remember past light-pollution contributors, such as the switch from mercury to high-pressure sodium lighting 30+ years ago. Eventually, the city started installing downward-reflective shields as they changed bulbs or performed maintenance.