Apologies in advance, as the archive is very basic and thus not terribly user-friendly at the moment. Each incident has a unique CHP ID which can help narrow your search.
CHP Incident ID's are structured as follows:
Where the values are as follows:
The two character CHP Dispatch IDs are as follows:
Using the archive:
The archive page list of all CHP Incidents for that day lists. Each link is an incident ID which you can use to help narrow your search. ex 200922BC00009
The 2 alpha characters in the middle of the incident ID (ex 191028BC01336) indicates which CHP dispatch center or communications center (BC, BG, GG etc.) which will help you narrow down the set of incidents where you may find what you're looking for. You can find a list of CHP dispatch centers here. If you hover your mouse over the links on the dispatch page you can see a link like this:
The last 4 characters "FRCC" (above) are what you're interested in. The first two characters are used in the ID of the incident so for example this incident is from the Fresno dispatch:
Dispatch centers and communications centers are different and the latter don't have these sorts of links but are fairly guessable like CHP Border Communications Center is "BC" like in the example above.
The incident numbers within a dispatch center increase with time so the further down the page are later in the day _within a group_.