Aren Cambre's Praxis Research

I can report even more TxDPS progress.

It turns out the problems pictured in the prior entry are for tickets were written on I-20 Business in or near Odessa:

What's going on here is I have a C# program that correlates each TxDPS ticket with a TxDOT reference marker. TxDOT's data has GPS coordinates.

These tickets on the left side of the picture were written at I-20 Business's reference markers. These markers have the same numbers as I-20 mainlane mile markers several miles east of Abilene, on the right side of the picture.

Why are the same numbers so far apart?

As explained in prior entries here, all Texas roads except Interstates use a reference marker system.

A road's reference marker increments only after the road crosses a gridline. This is on a grid superimposed on the state. These reference markers don't exactly indicate a mile of pavement unless the road direction is exactly N/S or E/W.

Texas Interstates use a mile marker system, where each mile of roadbed = 1 mile marker.

While "I-20 Business" in and near Odessa has "Interstate" in its name, it is in fact part of the state highway system. It is not part of the Interstate system or even the US highway system. So these Interstate business spurs/routes/loops use the reference marker system instead of the mile marker system.

It's just coincidence that the I-20 Business reference markers' numbers were matching Interstate mile marker numbers from many miles away.

I thought I had designed my reference marker locator C# program to only find reference markers within the same county. Turns out I had only done 1 of 2 steps needed to make this happen. After correcting the program and letting it run another 9 hours, I have much-improved data.

But I still found problems. An example is in Beeville, TX, where you have US 181 and US 181 Business. In the image at right, the business route appears on the left, and the main route appears on the right.

(What's with the J? It's actually Business US 181-J. Each business route along a road--and there can be several if the main road bypasses towns--has its own, unique letter suffix.)

While both these roads use the reference marker system, their numbering isn't parallel. For example, notice how the business route's reference marker 570 is parallel to markers 590/588 on the main route. This is an example where the system is not always contigious, although that doesn't matter much because I do have reasonable latitude and longitude for each reference marker.

Back to the point: if a ticket was written at the business route's reference marker 570, the TxDPS ticket data says it was written at US 181 rm 570. If this is all the TxDPS data gives me, how do I know if this refers to the US 181 business route rm 570 or the US 181 main lanes rm 570? While the main lanes' rm 570 is a few miles north, they are both in the same county. So my prior scheme, where I only match reference markers in the same county, can't handle this.

I scratched my head for a few hours until I stumbled on a strangely-named field in the TxDPS data. Turns out that this field has the route's TxDOT prefix! For tickets written on this business route, the field contains BU. For tickets written on the main route, it has US. Excellent!

So I went back to Odessa, where I had the original problem with I-20 Business. Well, it's better but still inconsistent: I'm seeing both IH and BI prefixes on I-20 Business. So looks like I need to sample a lot more routes to see if this is a systemwide problem.

While re-checking Odessa, I found something really weird: there's a gigantic number of tickets near I-20 and FM 2227, and they are all clustered on the northeast side of the intersection:

What??

I zoomed in more and added back the road prefix label:

Huh?

I inspected the area and saw no roads or anything special except--a DPS office! Yup, DPS officers appear to be waiting until they get back to their station before filing tickets.

I haven't found a rhyme or reason for this. All I can ascertain at the moment is only about 4 of these are speeding tickets, which is unusually low. So far, it appears speeding tickets are a large plurality, possibly a majority, of traffic-related tickets.

There's got to be another reason why they are filing at the station. If I'm lucky, these will mostly be non-traffic offenses and therefore not in my research.

Now I need to re-tweak my TxDPS reference marker locator C# program tonight thanks to the discovery of this new field. Tomorrow morning, I will have even better reference marker matching.