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Proof Safety Inspection Works

safety inspections

Pennsylvania is considered to have one of the most intensive safety inspection programs in the country. However, due to the common misperception that the program has little or no value to society or consumers, some legislators in the state feel the safety inspection process is no longer necessary. Added to the perception are some government reports indicating that the vast majority of vehicles successfully pass inspection requirements. In fact, legislators are claiming there is only a 2% failure rate. It is important though to note that during the inspection process, vehicles may initially fail, receive the necessary repairs, and then pass.

But where are legislators getting this information that only 2% of vehicles fail safety inspection? We’re not really sure. However, we do know that, in 2007 PennDOT hired Cambridge Systematics to perform a study on the safety inspection program. Through the four years of data they surveyed, they estimated 1-2 fewer fatalities per billion vehicle miles traveled for any state having a safety inspection program, determining the program is effective. However, in 2008, a study sponsored by North Carolina legislators, determined that “no evidence exists showing the safety program is effective.” In the performance of the current study, no paper was found to review actual safety inspection pass or fail rates.

According to The National Highway Traffic Safety Administration (NHTSA), vehicles have “never been safer.” With this statement more and more legislators are attempting to modify their states’ vehicle safety inspection programs. Researchers at Carnegie Mellon University recently completed a study on Pennsylvania’s safety inspection program. The initial findings show that while some newer vehicles do in fact have higher safety ratings, and technology has vastly improved over the past 10-20 years, yearly maintenance is still incredibly important to keep vehicles functioning as safely as possible; therefore, safety inspection programs are still very much necessary.

Vehicle safety inspections in Pennsylvania include checking vehicle components such as: steering/suspension, exhaust, fuel, body/doors/latches, glazing/mirrors, brake systems, lighting, tires, and other. The “other” category includes all or some of the following categories: wipers, bumper, defrosters, battery hold-down, brake warning lights, odometer, speedometer, etc. In order for a vehicle to pass safety inspection, their components must be within the allowable thresholds determined by PennDOT.

Final inspection statuses consist of:

Pass (Pass) – all tested components are within the allowable threshold. Vehicle receives sticker.

Pass with Maintenance (Fail, New, Repair, Adjust) – one or more components identified during the inspection require maintenance. Required repairs are performed and vehicle receives sticker.

Fail (Fail, New, Repair, Adjust) - one or more components identified during the inspection require maintenance. Required repairs are NOT performed and vehicle DOES NOT receive sticker.

*official designations in parentheses

The need is further proven the more you delve into the study. Researchers obtained information from CompuSpections and the e-SAFETY program. They compiled the information into the following parameters to analyze failure rates: urban/rural county classification, age, and odometer reading. They collected data from 2008 to 2012 from both sources, as well as received Pennsylvania vehicle registration records as of March 2012 and November 2013; no information pertaining to the vehicle owner or drivers of the vehicle were identified or released. Once all the data was reviewed and compiled the researchers at Carnegie Mellon University were able to analyze about 9 million light duty vehicles. The information gathered was then broken down in three different ways to determine failure rates.

Failure by Age

Evaluating the overall state failure rate was compiled by two different methods. The first was by combining the failure rate by age and the vehicle distribution in the registration dataset. This method resulted in an 18% failure rate. The second method was to combine the failure rate by age and the inspection vehicle distribution (Figure 2).

In this method, the overall failure rate was calculated to be 12%. Therefore, it was determined the failure rate for the state to be between 12% and 18%, or more specifically, in 2012, 1.4-1.7 million vehicles would have failed (Figure 3 further outlines this).

Failure by Odometer Reading

Figure 4 displays the failure rate based on odometer readings. When following this figure, you will see that the failure rate peaks in the 125,000 to the 150,000 miles range, reflecting a failure rate of 24.5%. Again, failure rates for new vehicles (with odometer ranges from 0-5000 miles and 5000-10,000 miles) have, on average, a failure rate of 3.3%.

Failure by County Types

The last way in which failure rates were determined was by breaking the information down by county types. While the results are different from the other two reviews, that are also fairly consistent in comparison, with a failure rate of 11% to 15% (Figure 5). These rates are a bit lower than the previous methods reviewed due to the higher composition of new vehicles in the inspection databases (sample) in comparison to the registration database (actual fleet). While this range is lower than the previous average range, it is still much higher than the commonly reported 2% failure rate.

This study focused on observing the safety of vehicle components. The researchers identified vehicle safety in terms of vehicle maintenance by analyzing failure rate trends over time. They illustrated their findings in Figure 6 by showing the failure rates followed for a given model year vehicle as it aged.

It is important to note that in all of these findings and on all of these figures, even the newest of vehicles don’t all pass safety inspection. It fact, it was determined that the average failure rate for vehicles considered to be one-year-old (based on miles driven) was 3.3%. And on average, vehicle inspection failure rates are between 12-18%. Both of these figures are much higher than the previously reported 2% often touted by policymakers.

The study made a point of explaining the importance of the effects of the safety inspection program. Without the program currently in place, it is estimated that up to 1.9 million vehicles would be on the road in Pennsylvania alone that need adjustments or replacements in order to be considered safe. But, because vehicles must have a valid safety inspection permit in order to be driven, owners will repair the necessary components.

Executive Director, Jeff Walter, says, “This report proves that annual safety inspection programs, such as Pennsylvania’s, are good for the driving public and make our roads safer. Legislators hopefully will look at the statistics in this report and see the benefit of safety inspection programs. In order to keep driving conditions safe, safety inspections must continue to be the necessary standard for all vehicles.”


D. Peck, H.S. Matthews, P. Fischbeck, and C.T. Hendrickson. “Transportation Research Part A,” Transportation Research Part A, vol. 78,no. C, pp. 252-265, Aug. 2015.

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