All Railroad Quiet Zones in the City of Boulder Officially Established as of April 30 Beginning at 7 a.m. on April 30, all railroad “Quiet Zones” work will be completed and the following railroad crossings will be officially established as Quiet Zones: 47th Street 63rd Street (north of Arapahoe Avenue) Pearl Parkway Valmont Road (established since 2019) Quiet Zones address the impact of train horn noise on surrounding neighborhoods and businesses through physical infrastructure that allows train engineers to pass through railroad crossings without needing to sound train horns. Train engineers still have the authority to sound the horn if unsafe conditions exist.