Motorist alerts TxTag to occasional double-charges in ORT lanes in Austin Tx

TxDOT should give Marcus Davis a reward of six months free tolls or somesuch. He alerted them to a toll system problem that occasionally double bills motorists in their open road toll (ORT) lanes.

Davis has a good sense of numbers. He told KXAN television in Austin - which broke the story - he sensed he was being overcharged by TxTag, the TxDOT unit that issues the sticker tags and operates the toll system accounts in Central Texas.

"I don't use the toll roads all that much, but I use them occasionally. And so I figured I had a low balance, but it shouldn't have been as low as it was," Davis told the TV reporter.

He combed through a printout of his account and sure enough found two almost identical tolls for SH45 westbound lane 10 Lake Creek plaza. He emailed TxTag and got a refund of the toll but decided to go public with the problem and contacted the TV station. He figured it might affect a lot of motorists.

The open road toll system uses a couple of in-pavement loops in each lane to track each vehicle through the toll read zone. Even though two lanes' loops could detect the same vehicle (straddling lanes) the logic of the algorithms is only supposed to generate one transaction per vehicle pass. The readers on the gantry above read each tag (aka as a transponder) by RF data signal multiple times within the read zone (three to six times is probably most common) but they must only associate one tag read with one vehicle pass as defined by the vehicle detection and tracking system, which in this case uses the electromagnetic loops in the pavement underneath.

Somehow the Central Texas Turnpike system has been occasionally seeing a second pass almost simultaneously with the first, it appears, generating two transactions where there should be only one.

A TxDOT spokesman Gabriela Garcia is quoted as saying they estimate the double pass/double transaction problem has been occurring about 150 times per day on their system which does about 190,000 transactions per day.

It is either a pavement loops problem or more likely a toll management software problem because it wasn't peculiar to Lake Creek. Double charges have turned up sporadically all over the system which covers SH130, SH45 and Loop 1.

UTS system

System integrator for this Central Texas TxDOT system was United Toll Systems (UTS) based in Wetumpka (near Montgomery) Alabama. UTS developed their own loops together with a digital signal processing that allows them to identify vehicles through matching electromagnetic signatures of different classes of vehicles.

UTS also did Miami Dade Expressway's toll system, though UTS have told us in the past that they had to almost completely start from scratch with designing the Central Austin system. UTS's contract provides for several years of maintenance and operations.

COMMENT: Reporters misreport. The announcer who introduced the TV report said "some lanes (in the Central Austin system) are charging double." This was doubly mistaken. The lanes weren't doublebilling everyone as this suggests. Also the problem was not "some lanes" it was the overall toll management system or the loops' logic.

And the reporter said the system was "prone to double charge." Prone to suggests likely to, but for any individual motorist the likelihood was 150/192,000 or a chance of less than one in a thousand of being double-billed. That's prone to occasional double billing, not prone to double billing.

150 times per day on a system with 192,000 transactions is a relatively small problem but, still, it shouldn't happen. Now they are alerted to the problem and know what to look for they should be able to figure out why it's happening and be able to fix.

It may well be fixed as we write.

Other TxDOT systems such as SH121 north of Dallas and Loop 49 in Tyler are quite different from the Central Texas Turpike System with system integration by Raytheon, which now has an umbrella contract to do new toll systems for the state tollroads, many of which are handed on to regional toll authorities after they are built. Austin's 183A tollroad in the northwest of the area run by the Central Texas Regional Mobility Authority had a toll system designed by Caseta Technologies.

Every system will have glitches, whatever they tell you. The glitch issue is: how serious, how many, and how quickly they are detected and fixed.

MAYBE BE UPDATES

TOLLROADSnews 2007-09-23