Mass Pike source of bad news even when it's no news (MEDIA)

Boston Herald recently (8/11) led off a frontpager: "Tens of thousands of Turnpike motorists have been socked with falsely inflated Fast Lane bills because the company that provided their transponders violated its multimillion-dollar contract by failing to inspect the system, a state audit has found. (Fast Lane is the Massachusetts Turnpike's brandname for E-ZPass IAG compatible electronic tolling - editor)

"State Auditor Joseph DeNucci - who investigated the overcharges after a front-page Herald expose in February - found that Fast Lane provider TransCore failed to inspect transponder equipment over the past two years as mandated in its $11 million-a-year contract."

We've nosed around a bit on this story.

It turns out TransCore asked to schedule the inspection of electronic toll equipment but Turnpike Authority officials had higher priorities - like a collapsed ceiling in the I-90 Big Dig tunnel, battles with the governor, difficulties getting support for a toll increase, a raft of maintenance issues that couldn't be funded, threats of expensive bond rating downgrades, and an ongoing financial crisis. The routine inspections slipped by.

The Authority never gave TransCore the OK to do the regular inspection. They aren't permitted to do a survey of equipment without a Turnpike Authority OK and dates and times when they can do the work.

Turnpike officials say there was no violation of the contract which only required the inspection when authorized. They say the lack of a survey of accuracy had nothing to do with toll system inaccuracies.

They say the equipment was working to specification.

When finally the inspection was performed earlier this year the equipment was found to be working within required levels of accuracy.

"Tens of thousands" in the Boston Herald piece sounds a lot of people being overcharged. In fact the Turnpike sampling suggested 114k out of 119m annual transactions. That is an error rate of just under one in a thousand, actually 0.096%.

The contract provides for accuracy of 99.5% while in fact the equipment was working at an accuracy of 99.904%, well within specifications. Contract specifications allowed up to 0.5% errors or 595k out of 119m/yr v the 114k estimated to have occurred.

Auditor screws up

The state auditor screwed up in one part of his report in saying (p3, 7 lines up) that the toll equipment was "failing to perform to specifications." In fact its accuracy was well over the specified accuracy required in the contract.

Errors would have had to be more than five times the level they were (595k/114k=5.2x) to have been in breach of contract specifications.

Vehicle separation in congested toll lanes

The problem embedded in an allowance for 0.5% errors is the industry-wide issue of vehicle separation in heavy traffic conditions - detecting the airspace between vehicles with a laser scanner or light curtain. Where the equipment doesn't 'see' the space it counts two cars, for example, as one 4-axle vehicle.

This is a chronic problem in toll systems in slow moving lanes in which cars queue and are nearly bumper to bumper, especially when some are quite high vehicles like SUVs and vans. Geometry of sight lines makes it tough to get a view between.

An undercharge for every overcharge

Left unstated in indignant-toned reports like that of the Boston Herald is that the errors cut both ways. For every overcharge due to counting extra axles on the car in front, there is an equivalent undercharge.  The vehicle behind doesn't get tolled if the equipment sees it as an extension of the vehicle ahead.

The motorist's chances of getting overcharged are equal to their chances of getting undercharged.

It's unfair to those overcharged, sure, but your odds of being socked too much equal your odds of getting a free ride.  

The toller isn't making any money out of the errors as the indignant tone of Herald style reporting suggests.

(NOTE: this account is oversimplified and possibly wrong. See correction here:

http://www.tollroadsnews.com/node/4306 2009-08-17 12:05)

"Equipment malfunctions" are usually a simple matter of grime accumulating on the light curtain glass or vehicles following one another so closely that the laser doesn't read the space between them because of vehicle shapes blocking a view of the 'air' between.

state auditor's report:

http://www.tollroadsnews.com/sites/default/files/Auditor.pdf

An argument for open road tolling and management

The problem of getting high vehicle separation accuracy in dense queued toll lane conditions is another argument for open road or all-electronic tolling and for traffic management with variable toll rates. Free flowing traffic at highway speed has vehicles consistently further apart and they are much more accurately separated by the toll equipment.

TOLROADSnews 2009-08-13 CORRECTION 2009-0817 12:05