Four in the morning on Denver's north side, and the streetlights still hold their orange hush over Chaffee Park and Regis. D & B Outdoor Services is out in it, moving the upslope snow that stacks against the city when a storm swings in off the northeast plains and refuses to leave. Driveways get opened wide enough for a real car, walks get scraped down to bare concrete, and the shaded stretches get treated before the midday melt can refreeze into glass. By the time the sky goes pale over Berkeley Lake, the block is passable and nobody has to think about it. That is the aim every single time: a street that behaves like an ordinary Tuesday.