BOULDER — Beginning at 7 a.m. Friday, all railroad “quiet zones” work will be done, and residents and businesses near the designated zones will hear train-horn noise less frequently. In a written statement, the city of Boulder said that five streets that intersect with the Burlington Northern Santa Fe railway in the city are affected by the new quiet zones and the signage or technology used to keep the crossings safe without the use of train horns. The zones are: 47th Street. 63rd Street (north of Arapahoe Avenue). Pearl Parkway. Valmont Road (established since 2019). Designated quiet zones permit train engineers to pass through railroad crossings without needing to sound train horns. Engineers still have the authority to sound the horn if unsafe conditions exist.