Data & methodology

Source

CrashGuide uses three named public sources: the California Highway Patrol Computer-Aided Dispatch feed, San Francisco Police calls for service, and the California Crash Reporting System (CCRS). Every incident page identifies its own source. We poll CHP roughly every 75 seconds and San Francisco about every ten minutes. CCRS is not a live feed: a separate daily job reconciles its trailing 120 days because filed reports commonly arrive weeks after a collision and can later be revised. We identify ourselves to the source servers and, for CHP, record what we observe while our collector is running: when an incident was first seen, the dispatch log updates that appeared, and when it cleared. Because this depends on polling, an update posted and withdrawn between two polls — or during any interruption on our side — will not appear here, so a timeline is what we observed rather than a guaranteed complete history. CHP's public live page does not provide a searchable historical archive; once an incident scrolls off it, it is no longer available there. CrashGuide preserves what it captured.

Enrichment

We resolve each incident's county and city with the U.S. Census Bureau's geocoder, parse roadway and cross-street from the dispatch location string, and identify the likely reporting agency (a CHP Area office for most freeway incidents; a local police department for many city-street incidents). When coordinates cannot be confirmed at high confidence, maps show an approximate area rather than a precise pin.

Known limitations

CHP and San Francisco call data can be preliminary and may be revised. CCRS is a maturing archive, so recent weeks are incomplete; historical totals end at a data-derived completeness cutoff. Severity means what the named source recorded; it is not an independent medical conclusion. A cited Vehicle Code section is not proof of fault, negligence, or conviction. Nothing on this site is an official record; official collision reports are available only from the investigating agency.

What we never publish

We do not ingest or publish CCRS person-level fields. We also do not publish names, plates, driver's-licence numbers, phone numbers, or other personal identifiers. Sensitive San Francisco calls are excluded entirely, and every structured free-text value is passed through the same personal-identifier filter used for CHP dispatch text.