Tx DPS is mostly Vhf-high P25 conventional, although in many areas they are heard more on the radio systems of the counties they patrol than they are on the state frequencies. In some areas, such as Tyler (off your path), and Waco (which
is on I-35), you'll also catch them on regional trunked systems at times. For the Waco & Tyler area, you might hear them on the
TxWARN P25 TRS. (I hear the Tyler units occasionally on this, via the Kaufman County tower.) There are also DPS talkgroups on the
GATRRS system in the Austin region. No idea how much DPS usage there is on that system; haven't been down there in a long time.
You would need a digital scanner, preferably NAC capable. Looking at the database
page, it looks like a ton of frequencies, but when you look closer, you'll see the same ones are used repeatedly with a handful of NAC codes. If you load the frequencies in the top section, Statewide APCO-25 Channel Plan, you'll get most of them. There are a few other location specific repeaters. These are numbered as DPS RPT XX, where 'XX' is a number higher than
20. For an example of this, look at Richmond, under the Pierce sub-heading for DPS-Houston. That shows as 155.53500,DPS RPT 28 Richmond - Dispatch.
For the counties, you'd need to check them out individually, and see if you wanted to program them. However, in many areas, such as here in the Dallas area, there is little traffic on the DPS frequencies. The troopers are primarily using their MDT's for routine stops, as well as license and vehicle checks.
