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Analysis: Study on speed limiters 'tortures' data into submission

A little more than a year after failing to reach a conclusion that speed limiters would enhance safety in large trucks, the group that prepared the study for the FMCSA has rewritten its final report to show the desired result. OOIDA says the changes, including points about limitations and uncertainties that were omitted from the final report, show bias and manipulation.

OOIDA and its research foundation compared the “draft final report” released in December 2010 and the “final report” released in March 2012 by the Federal Motor Carrier Safety Administration.

The two versions use the same data but show different conclusions about safety and speed limiters.

“We have reviewed the newly released report and noticed that no new data was used to draw this latest, reversed conclusion in comparison to the first draft in 2010,” OOIDA Executive Vice President Todd Spencer said.

“They threw out specific pieces of information that did not fit the biased agenda to impose speed limiters. So, it’s not even a new study at all, just new spin.”

A group called MainWay Services conducted the research, which included surveys and crash data collected from 20 truck fleets. MainWay collected data from 138,000 trucks and 15,000 crashes. A group of authors from various transportation institutions pulled the research together into the draft and final reports.

Discrepancies in the two reports are numerous. The 2010 version questioned the quality of the data, stating that, “… because of data limitations and data quality, the research team could not definitively attribute the effect to the presence of an active (speed limiter).”

Additionally, the 2010 version also questioned whether all crash data entered as “speed-limiter related” met the proper criteria as being related to speed limiters.

“These misclassifications or false positives can affect the validity of the results and the conclusions that follow,” the authors wrote in 2010.

Somewhere during the 15 months that followed, the story changed.

The questions about the data’s limitations and reliability were stricken from the final report. In their place are new quotations such as, “The findings showed strong positive benefits for SLs,” and, “… terms of safety benefits, results indicated that trucks equipped with SLs had a significantly lower SL-relevant crash rate (approximately 50 percent) compared to trucks without SLs.”

Spencer says the changes made in the reports shows an obvious speed-limiter bias.

“If you torture numbers long enough, they will confess to anything,” Spencer said. “That’s apparently what’s been done here – and when the numbers couldn’t be tortured enough, they were simply discarded.”

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