Caltrans lane and road closures physically in place RIGHT NOW.

Data: the Caltrans Lane Closure System (LCS). Only closures that crews
have actually established (CHP code 1097) and not yet picked up are
returned - scheduled-but-not-started closures are excluded, so this is
"what is blocking lanes now", not a construction calendar.
Refresh: 5-minute cache over per-district Caltrans feeds.

Filters: route (e.g. "I-80", "US 101", "1"); district (Caltrans district
1-12, e.g. 3 = Sacramento/Tahoe, 4 = Bay Area, 7 = Los Angeles);
center "lat,lon" with radius_km - closures whose begin or end point is
inside the circle. For a town or place, center is the filter that
catches work on EVERY road around it, including small state routes.

Read closure_class on each record, it is what the closure means for
through traffic:
- "full-roadway": the road itself is closed in that direction. The only
  class that means "you can't drive through".
- "ramp": a ramp or connector is closed (even when the raw record says
  "Full", that means the ramp is fully closed, not the highway).
- "one-way-traffic": alternating single lane with flagging; passable
  with delays. Common on two-lane mountain roads.
- "alternating-lanes", "moving", "traffic-break": rolling or brief work;
  minor delays.
- "lane": some lanes closed; the lanes field says how many of how many.
estimated_delay_minutes is present when crews reported one.
Shoulder-only work is excluded entirely.