VEHICLE ROADWORTHINESS AND ACCIDENTS

by Michael Paine, Vehicle Design and Research

Submission to the Victorian Parliament Road Safety Committee, 19 April 2000

Executive Summary

This report gives an outline of roadworthiness issues in Australia. Key points are:

Inspection programs and strategies vary considerably between Australian states and territories.

Various overseas studies into the effectiveness of inspection programs tend to be inconclusive. Although the effects are small and are usually swamped by other factors, the costs of efficient inspection programs can also be small. This makes benefit cost studies too sensitive.

Pilot studies with roller brake testers in NSW suggest that about 1 in 10 cars has serious service brake faults. Most brake faults are not readily detected by conventional road tests or visual checks. Contaminated brake fluid is also a problem.

Vehicle defects contribute to crashes to a much greater extent than suggested by police statistics. Police investigations tend to assign "blame" but overlook the contribution of defects to crash severity.

In depth studies suggest that vehicle factors, particularly defects, are "causal, possibly causal or contributory" in at least 12% of all crashes. Rates for older cars and heavy vehicles tend to be much higher.

Vehicles involved in crashes are much more likely to have serious defects than the general population. In these cases the defects did not necessarily "cause" the crash (they might simply be an indicator of a high risk operator). However, serious defects are likely to come into play during the demanding circumstances of a crash and make the crash more severe.

There is a very wide range in effectiveness of inspection programs around the world. Not all are effective at eliminating vehicles with serious defects.

Decentralised programs such as the NSW Authorised Inspection Station Scheme tend to be convenient for vehicle owners and popular with the motor repair industry but it is considered that the scheme is too cumbersome to manage and inspections are too thinly spread to ensure that quality inspection are conducted. In particular, vehicles in poor condition tend to gravitate to less scrupulous AIS.

Centralised programs used dedicated inspection stations with specialised equipment (particularly roller brake testing machines). Inspection quality can be much higher than with a decentralised system. Roadworthiness inspections can be efficiently combined with emissions testing in a centralised program.

Random inspections, either by "invitation" to attend an inspection station or by roadside selection, are a very important component of an effective inspection system. These should apply to cars as well as trucks and buses.

My recommended approach is to have a centralised program with several dedicated roadworthiness/emissions inspection stations that do periodic inspections of heavy trucks, buses and older cars and "invitation" inspections of randomly selected newer cars. These would be supplemented by a program of random roadside inspections, using portable roller brake testing machines.

CONTENTS

(click on asterisk to jump to page)

Introduction *
Current inspection systems in Australia *
Influence of vehicle inspections on roadworthiness *

Centralised versus Decentralised Inspections *
Brake Testing *
NSW Crashed Vehicle Study *
National Guidelines for Grading Defects *
Crash risk and serious defects *
Older vehicles and safety *

VEHICLE INSPECTION SYSTEMS AND THEIR EFFECTIVENESS *
THE COST-EFFECTIVENESS OF VEHICLE INSPECTION SYSTEMS *
SCOPE FOR FURTHER INFORMATION *
SUMMARY *
ACKNOWLEDGEMENT *
REFERENCES *
Appendix -Proposed Crash Contribution Factors *

Introduction

This document includes extracts from reports about roadworthiness prepared by Vehicle Design and Research over the past decade. It has been prepared to give an outline of roadworthiness issues in Australia.

Current inspection systems in Australia

In the state of Victoria there are no systematic, "periodic" motor vehicle inspection systems. Passenger vehicles are subject to compulsory technical inspections to assess roadworthiness on change of vehicle ownership. In addition, vehicles may be subject to random roadside inspections by police to check whether they pass roadworthiness criteria.

In New South Wales, inspection strategies are different for light and heavy vehicle categories. This is because of the very high distances covered by heavy vehicles and their much greater damage potential in road crashes. Further, the incidence of mechanical defects in heavy vehicles in NSW has been earlier shown to be very high, perhaps as high as 25% in the absence of any effective inspection strategies.

The Roads and Traffic Authority (RTA) in NSW now conducts both annual and roadside inspections of heavy vehicles, with even more frequent inspections for taxis and privately owned buses. In contrast, however, the trend for light vehicles (cars, light commercial vehicles and motor cycles) is to fewer inspections. This is based generally on the belief that the benefits expected from frequent periodic inspections do not outweigh the costs. Currently vehicles are inspected annually, but not for the first four years after the initial registration.

A summary of light vehicle inspection requirements for the different states in Australia is given in Table 1.

Table 1 - Summary of light vehicle inspection requirements in Australia

(source: Duignan et al, 15th ESV, 1996)

 
 

Influence of vehicle inspections on roadworthiness

USA

In 1989 the US National Highway Traffic Safety Administration published a report "Study of the Effectiveness of State Motor Vehicle Inspection Programs" (NHTSA 1989).This study included a literature review of the effectiveness of inspections in improving vehicle condition. The study found that there was a wide range in the quality of various state programs and that the better quality programs lead to better-maintained vehicles. Detailed results were:

Table 1: Effect of Periodic Inspections on Vehicle Condition

 
 

Evidently the type of audit inspection conducted varied between each of these studies. This difficulty is explored later in this report.

The NHTSA study also refers to a "before and after" study when annual inspections were discontinued in Idaho. "Brakes, steering, suspension and power train components were somewhat worse [after annual inspections ceased] while body components (lights etc) were about the same". For these tests a mobile inspection van was set up in a parking lot and vehicles were recruited on a "drop-in basis".

New South Wales Heavy Vehicle Inspections

The NSW Roads and Traffic Authority recently released the results of its "Heavy and public passenger vehicle roadworthiness assessment program" (Taverner 1995). Heavy trucks, buses and taxis were randomly selected at numerous sites throughout NSW in 1992 and 1995. The aim of this program is "to audit the maintenance of vehicles and to ensure vehicles are in a fit and proper condition to use the road system". Factors such as vehicle age, type of vehicle, odometer readings, vehicle use and commodity carried, jurisdiction of registration and type of service were analysed. A total of 1939 were inspected in 1995, compared with 1885 in 1992. On average vehicles inspected in 1995, particularly buses, were in better condition than those in 1992. Differences between areas of the state were also noted.

Similar reports on heavy vehicle inspection results were produced on an annual basis by the RTA (and former Dept of Motor Transport) between 1982 and 1989, although the selection methods for roadside inspections were not necessarily random.

NSW pilot study of inspections in shopping centre car parks

In 1994 the RTA conducted a pilot study on inspections of light vehicles at shopping centre car parks. Vehicle Design and Research P/L managed that project, which identified objective inspection items that could be used as a measure of roadworthiness (including the use of a portable roller brake tester). Vehicle owners were approached as they returned to their car and were told they could have an immediate inspection or arrange an inspection at a later date. About half agreed to an immediate inspection and a total of 118 inspections were conducted at four sites throughout NSW (51% of people approached). Most people reacted positively to the request to present their vehicle for inspection.

Of the inspected vehicles only six were issued with defect notices but most cases were treated as cautions. 54% of vehicles had a defect of some type and 14% had at least one serious defect. One third had at least one brake fault (most of these could only be readily detected with a roller brake tester) and 11% had tyre defects. Water-contamination of brake fluid was found to be a problem in one third of the 54 vehicles tested with a hygroscopic meter.

Although the results were informative they cannot be regarded as representative of the NSW light vehicle fleet due to both the "voluntary" method of selection and the likelihood that vehicles intercepted in a shopping centre car park during a weekday might not be representative of the remainder of the fleet. The method was found to be demanding on resources, in terms of total person-hours per vehicle inspected, although the average time per vehicle inspection was on target at 15 minutes.

NSW study of brakes on light vehicles

Vehicle Design and Research P/L also managed a pilot RTA study of the performance of brakes on light vehicles. This involved setting up portable roller brake testers at eight petrol service stations throughout Sydney and inviting owners who fuelled their vehicles to have a "three minute" brake test. A total of 538 vehicle were tested. 19% failed one or more of the performance criteria (compared with 32% in the shopping centre study) and 8% failed the service brake test (compared with 9% in the shopping centre study). It was concluded that the methodology (which only looked at brake performance) would form a convenient measure of roadworthiness programs.

Vehicle inspections in the Australian capital territory

For several decades ACT motor vehicles underwent annual roadworthiness inspections. Beginning in 1980 the ACT government progressively phased out annual roadworthiness inspections for most types of vehicles. In 1991 only light vehicles older than 6 years required an annual inspection. In 1993 about 5% of light vehicles between 3 and 10 years of age were randomly selected for an annual inspection and all light vehicles over ten years old were selected. By 1994 only light vehicles over 10 years old required an annual inspection (this still covered nearly half of the vehicle fleet) but an informal system of "exemptions" was introduced, partly to reduce the length of queues. This involved an inspector checking vehicles in the queue and exempting some if there were no obvious defects. About half of the vehicles were exempted, meaning that about one quarter of all ACT light vehicles still underwent an annual inspection.

A targeted roadside inspection program began around 1992. "Random selection" roadside inspections were developed through 1993/94. It was not until December 1994 that records of these inspections were reliably available. Therefore, although ACT inspection programs have undergone significant changes there are no reliable data available on the effects of these changes on roadworthiness.

During 1996 VDR reviewed options for inspections in the ACT. The following is an extract from the project report.

Centralised versus Decentralised Inspections

A centralised inspection scheme is based on inspections being conducted by a limited number of stations which specialise in these inspections. A decentralised inspection scheme is based on many stations conducting inspections on a part-time basis.

The current ACT system is a centralised scheme and the NSW Authorised Inspection Station Scheme is a decentralised scheme. On the face of it the NSW AIS Scheme seems to have advantages for motorists and vehicle repair businesses. On closer evaluation, however, there are numerous problems with the AIS Scheme. These are described in the following table. The result is that there will always be a few percent of stations which do not conduct inspections according to prescribed standards. Unsafe vehicles tend to gravitate to these stations and receive a "pass" report. This defeats the main purpose of the scheme - to get unsafe vehicles off the road.
 
 

Centralised Vs Decentralised Inspections

 
 

Note that in the case of decentralised inspections, this table is based experience in NSW. With a brand new scheme, such as that proposed for the ACT, it should be possible to adopt measures which will avoid or reduce some of the problems with decentralised stations. These issues are covered in the following sections.

Brake Testing

A simple on-road brake test using a decelerometer such as a Tapley Meter (or its electronic equivalent) will not detect several crucial types of braking defects because such tests do not identify faults in the brakes of individual wheels. These defects could result in loss of control under extreme conditions such as braking in the wet or braking during long descents. In addition, the pass/fail criteria generally used by authorities are much too lenient for modern vehicles (this results from the need to accommodate older vehicles).

Faults in the brakes of individual wheels can be detected by measuring the performance of each brake using a machine such as a roller brake tester or by removing road wheels and, in many cases, brake drums and examining brake components. Removal of road wheels is time consuming and can be difficult with some vehicles (e.g. some Ford Lasers) because the brake drum cannot be removed without replacing oil seals.

Roller brake testers are recognised by many enforcement authorities throughout the world as the most effective and efficient method of checking brake performance. This experience spans several decades (Grime, UK 1957, Toyne UK ,1978, Radlinkski USA, 1989 and Vaughan, Australia 1993). In addition to the ACT, roller brake testing machines are now used in Queensland, New South Wales, Victoria and South Australia.

The authors have assisted the NSW Roads and Traffic Authority with a pilot study into the condition of car brakes using portable roller brake testers. Being a pilot study the results are tentative but they suggest that about one quarter of the cars randomly selected had serious faults with service brakes and required maintenance. It is unlikely that these faults would have shown up in on-road tests.

Another method of measuring individual brake performance is by use of skid plate testers. These are permitted under the NSW AIS Scheme but are rarely installed.

It is recommended that the new inspection arrangements require the use of roller brake testers or skid plate testers for testing vehicle brakes. On-road brake testing using a decelerometer is not an acceptable alternative to these devices and removal of road wheels is impractical.

NSW experience indicates that suitable roller brake testers for cars and other light vehicles can be supplied and installed for about $20,000. This setup cost is, of course, higher than that for the unsatisfactory alternative of a road test but a road test can be expected to take about 5 minutes longer than a roller brake test - this translates to an extra operational cost of about $50,000 per year for a station conducting 10,000 inspections per year. In other words, a roller brake tester could pay for itself in 6 months.

A brief survey of the condition of brake fluid by the NSW RTA revealed about one-third of vehicles had contaminated brake fluid with a very low boiling point. This can cause loss of brakes, particularly on long descents. It is recommended that brake fluid testing be included in the inspection standards.

THE ROLE OF VEHICLE DEFECTS IN CRASHES

Studies of the role of vehicle defects in crashes in Australia have generally been rather weak in their methodology and unreliable in results. Indeed any results have generally only been secondary to the prime purpose of the study.

One of the first was an in-depth on-scene crash investigation conducted in Adelaide South Australia between 1975 and 1979 (McLean 1979). The Adelaide study was conducted by two teams each consisting of a medical officer, a psychologist and an engineer. They attended 304 accidents in and around Adelaide and examined and cross-tabulated all aspects of the crashes. In regard to police reporting of accidents, only 50% of the cars involved were recorded as having been inspected, and in only 2 out of 386 cases were the defects recorded by the police relevant to the cause of the accident. No attempt was made to dismantle components during the vehicle examination, and searches for defects were not conducted as thoroughly as for other factors contributing to occupant injury. No brake performance checks were carried out. Subject to these limitations, the Adelaide study found that in about 1% of all crashes defects were directly causal in nature. In 5.4%, defects were possibly causal. The proportion of cars with one or more defects identifiable increased with age. These researchers also found that the reporting of defects by police was poor. The authors concluded that "on the basis of the data collected in this study there is no clear case for the introduction of periodic motor vehicle inspections but an expansion of the existing system of spot checks, concentrating on tyre characteristics, may be worthwhile".

In Sydney, a series of studies was undertaken in the Fairfield area during the middle and late 70s by the Traffic Accident Research Unit Herbert and Humphries, 1979). The identification of vehicle defects was not the prime purpose of the series, but in general it was found that about 1% of the light vehicle crashes were caused by vehicle defects with the contribution of defects to heavy vehicle crashes being much higher, at 10% to 50%.

In other countries there have been a large number of studies undertaken into the role of defects in crashes, extending over the last 20 or more years.

A very careful early in-depth crash investigation study in the United States was conducted by the University of Indiana (Treat 1977). Overall, this study found that vehicle factors were "definite, probable causal or severity increasing" in 12.6% (plus/minus 3%) of the 420 crashes studied. From the published data it can be derived that this percentage rose to 25% (plus/minus 8%) for vehicles in the 9-12 year age group and 50% for vehicles aged 13 years or more (although the sample size for older cars was very small).

A 1978 study in Melbourne was of a randomly selected sample of fatal and other crashes. A total sample of 347 crashes were investigated by a physician, a sociologist, a mechanical engineer and a traffic engineer. It was found that 5.8% of vehicles had defects that may have contributed to the crash including two vehicles that had smooth to bald tyres.

A major review in Europe was a report to the ECE by the German Technical Inspection Authority (TUV) (Rompe and Seul 1985). The TUV examined mostly European studies, but included some from the United States. The review concluded that vehicle defects were the most likely cause in 8.5% of accidents.

Sabow (1994) describes the results of crash investigations in Germany by DEKRA. "According to the official accident statistics, only some 2.5% of accidents are caused by technical defects. However, technical defects are difficult to detect at the site of the accident... in-depth studies... have revealed that technical defects are responsible or partially responsible for accidents to a far greater extent.". Technical defects were considered to have a significant influence in about 8% of car accidents and 20% of heavy commercial vehicle accidents. Also, during routine vehicle inspections, older vehicles were more likely to have serious defects (vehicles more than 8 years old accounted for 25% of the fleet but had 50% of the serious defects).

It is known that defects in vehicles contribute to crashes to a much greater extent than suggested by police statistics.

NSW Crashed Vehicle Study

A useful contribution to these rather dated statistics should available through the "Crashed Vehicles Study" by the Roads and Traffic Authority. Detailed data analysis for this study, which covered more than 3,000 accident-involved vehicles, has not yet been undertaken, although some early results were reported at the 1996 ESV Conference in Melbourne (Duignan et al 1996). Crashes were selected on a targeted random sample basis and include heavy vehicles. Investigations were conducted by trained vehicle inspectors. Throughout the vehicle inspection, emphasis is placed on the objectivity of measurements. The inspectors were provided with a comprehensive tool kit, allowing removal of vehicle components and measuring of any movement. Components in the following categories were inspected:

•driving controls;

•seats;

•seat belts and airbags;

•lighting and wiring;

•windscreen and windows;

•body condition;

•towing devices; couplings and loading;

•engine driveline fuel systems and exhaust;

•steering suspension;

•wheels and tyres;

•brakes;

•modifications.

Up to the date of the ESV presentation 224 crashes had been investigated. This was only 7% of the total target for the complete investigation. These crashes involved 437, vehicles of which over 90% were inspected. Those that were not inspected had either left the scene before the inspectors arrived or whose owners refused permission to inspect. In accordance with the planned quota system for the study, heavy vehicles were over-represented in comparison with NSW mass crash statistics.

Inspectors were required to determine if any of these faults contributed to the cause of the crash or its severity. Tentative indications are that the contribution of defects to crashes is about the same as that found in the studies reported by Treat and Sabow. The potential for further analysis of the NSW Crash Vehicles Study is discussed later. Note that all three studies (Treat, Sabow and RTA) covered vehicles in jurisdictions with periodic inspection programs. There do not appear to be any equivalent studies in jurisdictions without such programs.

As part of this project, VDR developed a set of "Crash Contribution Factors". These were intended to provide a link between the discovery of defects on a vehicle and the occurrence or severity of a crash. These factors are set out in the Appendix. To date they have not been used for analysing the Crashed Vehicle Study.

National Guidelines for Grading Defects

In February 1999 the National Road Transport Commission issued "Administrative Guideline: Assessment of Defective Vehicles". This was prepared for NRTC by Vehicle Design and Research. The Guideline includes the following description of the effects of vehicle defects. They may:

Impair the driver's view of the road.

Eg. scored windscreen, inoperative wipers in wet weather, missing mirrors and inoperative headlamps.

Impair the visibility of the vehicle to other road users or prevent the driver from indicating his or her intentions (conspicuity).

Eg. inoperative lights and inoperative horn.

Impair the driver's control of direction and/or speed of the vehicle.

Eg. steering, tyre/brake defects, insecure driver's seat.

Result in intrusion into other users' road space or undue danger or nuisance to others.

Eg. oil leaks, sharp projections, excessive smoke, excessive noise. Note that separate procedures apply to vehicles which exceed mass or dimension limits.

Impair the built-in occupant protection afforded by the vehicle in the event of a crash (crash protection).

Eg. missing or broken seat belts, insecure seats, weakened body structure.

Increase the risk of further injury after a crash has occurred (post-crash).

Eg. insecure fuel tank (risk of fire), inoperative emergency exits.

Inspection programs in Australia should work to these guidelines.

Crash risk and serious defects

Research on heavy vehicle crashes in the USA, and tentative results from the NSW Crashed Vehicle Study suggest that a crash-involved vehicle is more likely to have serious defects than a vehicle selected at random from the roadside. The US study found that articulated trucks involved in crashes had four times as many defects as those selected at random. Data for cars are not available but similar results can be expected.

The presence of defects does not, of course, mean that these defects contributed to the crash. Serious defects might simply be an indicator of a risky operator who skimps on roadworthiness and takes other risks that lead to higher crash involvement. However, as described in the previous section, defects are much more likely to have an effect on a crash when systems are under stress. For example, braking defects often do not become apparent until the driver places extreme demand on them and occupant protection devices such as seat belts are only tested to the limit in a severe crash. The point is that risky behaviour makes the crash more likely and the presence of defects generally makes the consequences of a crash more serious.

Older vehicles and safety

It is well known that the age of the Australian car fleet is increasing. On average an older car travels less distance each year than a newer car, but as the car population has aged the total distance travelled by older vehicles has risen both in absolute numbers and as a proportion of the total vehicle population. Consulting engineer Rodney Vaughan has published several papers on the effect of this aging population on the safety of the fleet. (See for example Vaughan 1993). He has shown that the occupant death rates in older cars is consistently higher than in newer cars. The reasons for this effect are not clear and relate not only to the increasing safety of newer cars (see below) ) but also to driver characteristics. Deterioration of structure and restraint systems might also play a role.

Recent vehicle models have been shown to be much safer, in terms of the risk of the occupants receiving severe injuries, than older models. Lie et al (1996) found that pre-1991 cars in Sweden had 50% higher risk of severe/fatal injuries than post-1991 cars. A recent study of real world crashes in Australia by MUARC (Haley 1997) came to similar conclusions: the risk of severe injury, once a crash has occurred, decreases steadily by year of manufacture. On average, cars manuafactured in 1982 had 30% higher risk than those manufactured in 1992. Cars manufactured in 1972 had twice the risk.

Recent safety improvements, such as airbags, are likely to result in further significant reductions in the risk of severe injuries to car occupants. There are, therefore, potential road safety benefits available from strategies which reduce the average age of the vehicle fleet.

Conversely, measures which increase the service life of vehicle may have an adverse effect on road safety. This has sometimes been used as a criticism of vehicle inspection programs on the basis that they may prolong the service life of older vehicles. This argument appears to be tenuous and probably derives from confusion with the advantages of preventative maintenance (that it can reduce the overall cost of repairs). It is thought that inability to pass an annual Safety Check is a major reason for scrappage of older vehicles in NSW. Subject to caution about numerous confounding factors, Australian data does support this assertion. According to Caldwell (1992), during 1991 the median age of cars in Victoria, which does not have periodic inspections, was 9.6 years compared with 8.25 years for NSW and 8.6 years for the ACT, both of which have annual inspections for older vehicles.

VEHICLE INSPECTION SYSTEMS AND THEIR EFFECTIVENESS

Vehicle inspection systems are a kind of audit of the fleet. They do appear to be effective in reducing the number of cars in the fleet with defects. However, there are several different kinds of vehicle inspection system, ranging from systems of low quality and high cost to those which are effective and modestly priced. However, it is not possible to assume that a system which is effective in one administration will be as effective if simply transplanted to another.

Essentially there are two tests of effectiveness for vehicle inspection systems. One is whether the systems decrease the proportion of vehicles in the fleet with defects. The second is whether by doing so they reduce the number of accidents caused by such defects.

A major study of the effectiveness of motor vehicle inspection programs in the states of America was released in 1989 by the US National Highway Traffic Safety Administration (NHTSA 1989). This review came to generally negative conclusions.

The study was of the effectiveness of state motor vehicle safety inspection programs in

(1) reducing highway crashes that result in injuries and deaths; and

(2) limiting the number of defective or unsafe motor vehicles on the highways.

A NHTSA task force reviewed relevant literature, studied existing Periodic Motor Vehicle Inspection programs (PMVI, as they are known in the United States), conducted site visits to selected PMVI and non-PMVI States, and analysed NHTSA's crash data bases. In addition, two public hearings were held and comments requested from the public through two separate notices published in the Federal Register.

It was found that there was no conclusive evidence in the literature that PMVI programs were, or were not, effective in reducing crashes. At that time, 21 States and the District of Columbia had PMVI programs. In the PMVI jurisdictions, there was considerable variation in the equipment items inspected and in the procedures, rules and regulations for inspections. Analysis of the Fatal Accident Reporting System (FARS) data and State accident data files failed to show any evidence in the accident data examined that would suggest that PMVI programs affect the crash involvement rates of older vehicles compared to newer vehicles. Analysis of data concerning vehicle component failures from the Crash Avoidance Research Data file (CARDfile) for four States indicated that non-PMVI States reported a higher percentage of old and new crash-involved vehicles with component failures. Tyre failures accounted for the majority of the increased percentage of component failures reported in the non-PMVI States. The task force found that PMVI was effective in limiting the number of poorly maintained vehicles on the highways. An attempt to correlate this with a reduction in crashes on the highways failed to show any significant effect of PMVI.

However, the next year the US General Accounting Office (GAO) evaluated the NHTSA report, after it had been criticised by various industry groups for not accurately representing the safety benefits of inspection programs.

The GAO responded that routine police accident reports tended to understate the number of accidents in which defective vehicle components contributed to the cause of the accidents. The GAO pointed to the relative consistency of studies showing reduction of vehicle defects, and argued that there must therefore be a reduction in accident rates from the inspection programs. Research studies had generally been hindered by the limitations of available accident data and the difficulty of accounting for the various factors that can affect accident rates. The use of fatal accidents for study was not entirely valid because of the low proportion of all accidents that were fatal and their generally untypical nature. While fatal accident rates were similar in states which had inspection systems to those which did not, total accident rates were 17% lower in four states using inspection programs compared to six states that did not.

However, the GAO concluded that while most studies pointed to a safety benefit from inspection programs they did not provide a reliable basis for judging how much effect the programs had on accident rates. They called for more research into these questions. In general, the conclusion of both these American organisations was that a reduction in accident rates was a possible consequence from a well conducted high quality vehicle inspection system.

The study in recent years that has most closely approached a valid experimental design was conducted in Norway and reported in 1992 (Fosser 1992). A total of 204,000 cars were randomly assigned to three different experimental conditions: 46,000 cars were inspected annually during a period of three years; 46,000 cars were inspected once during three years; and 112,000 cars were not inspected. The number of accidents was recorded for a period of four years. No differences in accident rates were found between the groups. However, the roadworthiness of inspected vehicles improved compared to those not inspected. The experiment did not have any unintended side-effects.

However, Vaughan has pointed out that there is at least one factor which precludes the application of these Norwegian results to Australia. Norway has a prominent program of random roadside inspections. This resulted in about 14% of the control group (no periodic inspection) being inspected at least once during the study period. The geography of Norway is such that random roadside inspections can be strategically effective. Therefore vehicle owner awareness of roadworthiness issues is likely to be much higher than in countries such as Australia.

In 1983 British Columbia (Canada) suspended its periodic vehicle inspection program of light vehicles. Since that time there have been a number of requests to reinstate the program. The management consulting firm KPMG carried out a comprehensive review of vehicle inspection programs for the Government during 1994 (Holdstock et al, 1994). The review looked at North American experience, as described above. Further analyses were conducted into age effects and cost-effectiveness models were developed. The researchers were unable to detect any significant statistical relationship between the number of fatal accidents and the presence of vehicle inspection programs but noted that the results lacked statistical power making it difficult to discern real relationships.

Two difficulties in applying the British Columbia review to Australia are that the evaluation by vehicle age did not take into account annual kilometres travelled and the cost-effectiveness study did not consider the option of only inspecting older vehicles. Annual kilometres travelled can have a substantial influence on the analysis. For example, based on 1992 Australian Bureau of Statistics data, vehicle built in 1991 travelled an average of 21,000km per year, those built in 1981 travelled an average of 13,900km per year (66% of the 1991 value) and those built in 1971 travelled an average of 8,000km per year (38% of the 1991 value).

THE COST-EFFECTIVENESS OF VEHICLE INSPECTION SYSTEMS

Given precisely the same data, organisations and individuals in Australia have come to diametrically opposed conclusions on whether periodic motor vehicle inspection systems are worth their cost or not.

For example, engineers in the NRMA in NSW have concluded that because studies are consistent in pointing to reductions in vehicle defects from periodic inspections, this justifies a conclusion that these programs do reduce accident rates, although the amount and quality of the data are inadequate to be more precise. In their opinion the inspection system in NSW should therefore be continued and its intensity maintained, although its efficiency could be improved by the use of dedicated well-equipped inspection centres, an increase in consistency of inspection standards and more use of random roadside inspections and tests.

On the other hand, the motorists organisation in Victoria, the RACV, comes to the conclusion that studies have found that periodic inspection programs have not proved to be effective in improving road safety as measured by crash involvement rates. In-depth crash investigations conclude that mechanical defects have a "insignificant" effect on road crash rates, with at most some 2% of crashes being attributed to mechanical defects. The RACV believes that the major cost of introducing an annual vehicle inspection program in Victoria would not even come close to being justified by commensurate benefits.

An American review, conducted in 1985 for the NHTSA, pointed to suspicions that the results of cost-effectiveness evaluations were coloured by pre-existing opinions, and that data were insufficiently reliable to come to firm opinions. The purpose of this review of 41 studies and reports concerning periodic motor vehicle inspection was to seek evidence as to whether the costs of requiring all motorists to have certain safety components on their vehicles inspected and repaired on a regular basis are less than the benefits gained from such inspections in terms of safer vehicles and fewer vehicle-defect accidents. The authors stressed that a number of studies had provided evidence that vehicles in some PMVI jurisdictions are in better condition on some components than vehicles in some non-PMVI jurisdictions, but none of these studies had involved truly random samples of vehicles-in-use. Similarly, a number of studies had reported some reductions in accidents in association with PMVI (and some had reported the opposite), but no credible evidence was found to demonstrate significant changes in vehicle-defect accidents as a result of PMVI.

Thus, in their opinion, the few studies which had addressed the cost-benefit question have tended to be rather subjective and speculative because of the shortage of thorough and believable research on PMVI effectiveness. There is credible evidence that existing PMVI programs are not as reliable in detecting degraded safety components and forcing their repair as was envisioned by PMVI proponents. It is clear that much more could be done to improve the effectiveness of existing PMVI programs. Also, they considered, auto manufacturers could do more to encourage the maintenance of safe vehicles by providing durable components and built-in indicators of their failure.

SCOPE FOR FURTHER INFORMATION

As indicated above, the NSW Crashed Vehicles Study has collected data that are highly relevant to the contribution of defects to crashes. Apparently the question of release of the data for road safety research has not yet been addressed by the RTA.

Once the data are available the following issues could be addressed:

(i) Are defects more likely to be a factor in crashes involving older vehicles?

(ii) Are the types of defects identified as contributing to crashes likely to be picked up by a periodic inspection? (And, did any appear to have slipped through the inspection process?)

(iii) Are defects more likely in vehicles which have recently been acquired? (i.e. Is inspection on transfer an effective strategy?)

It would be useful if an equivalent (but smaller scale) study was undertaken in a state without periodic inspections such as Victoria.

SUMMARY

In-depth crash studies tend to indicate that the contribution of defects to crashes is under-reported by Police. The current NSW Crashed Vehicles Study appears to be finding similar results to in-depth studies carried out in the USA and Germany. Those studies, covering vehicles operating in jurisdictions with periodic vehicle inspections, found that vehicle factors, particularly defects, were definitely causal, possibly causal or contributory in at least 12% of all crashes. The USA study found much higher rates with older vehicles but the age of the study (1977) and the small sample sizes of older vehicles mean caution should be exercised in the application of these results to present-day Australia.

Cost-effectiveness studies concerning inspection programs have tended to be rather vague and speculative. Given the same data, organisations have sometimes come to diametrically opposed conclusions. This situation probably results from uncertainty about both the contribution of defects to crashes and the influence of inspection programs on these defects. Subject to this uncertainty (and continuing the speculation) , the contribution of periodic car inspections to crashes is likely to be a few percent. Given the overall cost of car crashes in Australia, a saving of, say, 2% can translate into well over $100 million per year. There is scope to operate effective inspection programs within this figure.

Further analysis of the NSW Crashed Vehicles Study data should help to answer several questions related to the contribution of defects to crashes and the influence of periodic vehicle inspections on these defects.

ACKNOWLEDGEMENT

Extracts from an unpublished report co-authored with Dr Michael Henderson have been used extensively in this document. Dr Henderson's contribution is appreciated.

Numerous officers from the NSW RTA and ACT Department of Urban Services provided advice and assistance with the projects described in this report. Ray Gigg provided technical and supervisory support for several of these projects.

REFERENCES

Caldwell P (1992) Scene setting - the problems of the ageing vehicle fleet, Proceedings of the Wheels 92 Conference, Institution of Engineers, Australia.

Duignan P., Williams S. and Griffiths M., Vehicle Defects in Crashes, in Proceedings, 15th International Technical Conference on Enhanced Safety of Vehicles, Paper 96/S9/0/18, National Highway Traffic Safety Administration, US Department of Transportation, Melbourne 1996.

Grime G. & Lister R.D. (1957) Inspection of Vehicles for Roadworthiness, with Special Reference to Methods & Equipment, Proc. Institution of Mechanical Engineers, No. 5, pp129, London.

Fosser S., An experimental evaluation of the effects of periodic motor vehicle inspection on accident rates, Accident Analysis and Prevention, 24(6):599-612, 1992.

Haley J. Review of Vehicle Defects, Accidents and Safety Inspection Systems: A Discussion Paper, NRMA Chief Engineers' Department, NRMAssociation, New South Wales, February 1991.

Haley J (1997) Why you are safer in a new car, Open Road, NRMA, March/April 1997 [based on a MUARC report associated with the Used Car Safety Rating Program].

Holdstock J, Zalinger D and Hagarty D (1994) Review of a mandatory vehicle inspection program, study report for the Ministry of Tranpsortation and Highways, British Columbia, Canada.

Herbert D. C. and Humphries M., Fairfield On-scene Study of Collisions, Supplement to Three Quarterly Reports, Traffic Accident Research Unit Report 1/79, Department of Motor Transport NSW 1979.

Lie A, Tingvell C and Larsson P (1996) The crash safety of new car models - a comparative study of new versus old car models, in Proceedings, 15th International Technical Conference on Enhanced Safety of Vehicles, National Highway Traffic Safety Administration, US Department of Transportation, Melbourne 1996.

McLean A. J., Adelaide In-depth Accident Study 1975/1979, Road Accident Research Unit, University of Adelaide 1979.

NHTSA, Study of the Effectiveness of State Motor Vehicle Inspection Programs: Final Report, Report number: HS-807 468, National Highway Traffic Safety Administration, Washington, DC, 1989.

Paine M., Contribution of Vehicle Defects to Crashes: Literature and Research Review, Vehicle Design and Research Pty Ltd, for the National Road Transport Commission, Report G174, June 1994.

Radlinkski R (1989) Assessment of Experimental Methods for Determining Braking Efficiency, Proc 12th International Conference on Experimental Safety Vehicles, NHTSA, USA.

Rompe K. and Seul E., Final Report Commissioned by the Directorate General for Transport, 7/G2 of the Commission for the European Communities, TUV Rheinland, the Rheinland Technical Inspection Authority, 1985.

Sabow G (1994) "The influence of technical defects on accidents" , Proceedings of VIth World Congress of the International Road Safety Organisation, Cape Town, Oct 1994.

Toyne C.C.(1978) Official Inspection Procedures for Road Vehicles in Great Britain, SAE paper 780031, Warrendale USA

Treat J., A Study of Pre-crash Factors Involved in Traffic Accidents, HSRI Research Review, Volume 10 number 6, 1977.

Vaughan R., Car Aging and Safety, Journal of the SAE Australasia, July/August 1993)

Vaughan R.G. (1993) Safety Maintenance of Road Vehicles, Institution of Mechanical Engineers, Paper C444/007/93, London

Wolfe A. C. and O'Day J, Cost-effectiveness of Periodic Motor Vehicle Inspection (PMVI): a Review of the Literature, Report number UMTRI-85-4, University of Michigan Transportation Research Institute, for the National Highway Traffic Safety Administration, Washington, DC, 1985.

Youngman J. H. R. and Stolinski, Compulsory Periodic Vehicle Inspections: an RACV Viewpoint, Royal Automobile Club of Victoria Limited, Report CE94/1, June 1994.
 
 
 
 

Appendix -

Proposed Crash Contribution Factors

(Developed by VDR for NSW Crashed Vehicle Study)

------------DRIVERS CONTROL OF VEHICLE------------------------------------------
DRIVER CONDITION

DRIVER AFFECTED BY EXHAUST/FUEL FUMES
DRIVER FELL ASLEEP OR WEARY
DRIVER HEART ATTACK/MEDICAL PROBLEM

DRIVER CONTROLS

DRIVER MISREAD INSTRUMENTS
ENGINE FAILURE/STALLED
FOOT PEDAL NOT OPERATED CORRECTLY
SWITCH/STALK OR KNOB NOT OPERATED CORRECTLY
HAND CONTROL NOT OPERATED CORRECTLY
DRIVER FORGOT TO RELEASE PARKING BRAKE
DRIVER PROBABLY DIDNT APPLY PARK BRAKE

 

------------HANDLING AND BRAKING------------------------------------------------

BRAKING

BRAKE PERFORMANCE LESS THAN EXPECTED
BRAKE FADE
TOTAL BRAKE FAILURE
PARKING BRAKE FAILED TO HOLD VEHICLE
PREMATURE LOCKUP OF BRAKES UNDER MODERATE BRAKING
SKID/SPIN DURING HEAVY BRAKING (DRY)
SKID/SPIN DURING HEAVY BRAKING (WET)
TRAILER BRAKES INEFFECTIVE
UNUSUAL PRECRASH MANUOEVRE (BRAKING)
VEERED TO ONE SIDE UNDER BRAKING
HEAVY BRAKING ATTEMPTED
CLAIMED BRAKE FAILURE BUT NOT SUPPORTED
DRIVER UNABLE TO SELECT APPROPRIATE GEAR

DIRECTIONAL CONTROL

COMBINATION INSTABILITY (TRAILER SWAY)
LOSS OF DIRECTIONAL STABILITY/ROLLOVER (DRY, NO BRAKING)
LOSS OF DIRECTIONAL STABILITY (WET, NO BRAKING)
UNUSUAL PRECRASH MANOEUVRE (ACCELERATION)
UNUSUAL PRECRASH MANOEUVRE (CHANGE OF DIRECTION)
VEERED TO ONE SIDE IN HIGH WIND
JACK-KNIFE/TRLR SWING UNDER BRAKING
STEERING FAILURE

------------HAZARD RECOGNITION BY DRIVER----------------------------------------

DRIVER VISION

DRIVER FORWARD VISION OBSCURED (DRY)
DRIVER FORWARD VISION OBSCURED (WET)
DRIVER REAR VISION OBSCURED
DRIVER SIDE VISION OBSCURED
HAZARD NOT ILLUMINATED BY HEADLIGHTS (NIGHT)

WARNING SYSTEMS

DRIVER UNAWARE OF BRAKING FAILURE

---------- HAZARD RECOGNITION BY OTHER ROAD USER-------------------------------

CONSPICUITY

OTHER ROAD USER FAILED TO SEE SUBJECT VEH AT NIGHT

WARNING SIGNALS

OTHER ROAD USER FAILED TO DETECT BRAKING
OTHER ROAD USER FAILED TO DETECT INTENTION TO TURN

------------MISCELLANEOUS-------------------------------------------------------

AGGRESSIVITY

OTHER ROAD USER INJURED BY SHARP EDGE/PROTRUSION
UNDER-RUN
EXTERNAL ACCESSORY INCREASED DAMAGE/INJURIES

EXCESS MASS/DIMENSIONS

EXCESS MASS OR DIMENSIONS
EXCESS MASS CAUSED ROAD/BRIDGE FAILURE

LOAD SECURITY

OCCUPANT INJURED BY CARGO/GOODS ON BOARD
OTHER ROAD USER INJURED BY LOAD FALLING/FALLEN
LOAD SHIFTED
LOAD INSECURE

MECHANICAL FAILURE

COMBINATION SEPARATED
ELECTRICAL FAILURE
MOTORCYLE COMPONENT STRUCK GROUND WHILE CORNERING

------------OCCUPANT PROTECTION-------------------------------------------------

HAZARDOUS OBJECTS

OCCUPANT INJURED BY INTERIOR OBJECT (NOT GOODS)
STEERING COL MOVED REARWARDS AND CONTACTED DRV

RESTRAINT PERFORMANCE.

EXTERNAL ACC AFFECTED OCCUPANT PROTECTION
HEAD RESTRAINT FAILED
OCCUPANT HIT HARD OBJECT DESPITE AIRBAG
OCCUPANT CONTACTED HARD OBJECT DESPITE SEAT BELT
OCCUPANT CONTACTED ROOF DESPITE SEAT BELT
OCCUPANT CONTACTED SIDE OBJECT
NO CONTACT BUT OCCUPANT INJURED WEARING SEAT BELT
SEAT ANCHORAGE FAILED
SEAT BACK FAILED
SEAT BELT FAILED
OCCUPANT EJECTED

RESTRAINT USE

UNRESTRAINED OCCUPANT (NO SEAT BELT AVAILABLE)
UNRESTRAINED OCCUPANT (NOT WEARING AVAILABLE S/B)

------------OTHER---------------------------------------------------------------

OTHER FACTORS
BUS DOOR PROBLEM

------------VEHICLE INTEGRITY---------------------------------------------------

GLAZING

OCCUPANT INJURED BY BROKEN GLASS
OCCUPANT INJURED BY UNBROKEN GLASS (EDGE)

INTRUSION

OCCUPANT INJURED DUE TO FRONTAL INTRUSION
OCCUPANT INJURED DUE TO REAR INTRUSION
OCCUPANT INJURED DUE TO SIDE INTRUSION
OCCUPANT INJURED DUE TO TOP/UNDERSIDE INTRUSION
ROOF CRUSHED

RESCUE HAMPERED

VEHICLE FIRE
DOOR JAMMED AFTER CRASH - HAMPERED RESCUE

STRUCTURAL FAILURE

CAB TITLED FORWARD DURING CRASH
DOOR OPENED DURING CRASH
MASSIVE DEFORMATION OF VEHICLE BODY
VEHICLE BROKE APART IN CRASH
BODY SEPARATED FROM CHASSIS

c2000 Vehicle Design and Research Pty Ltd
May be reproduced with acknowledgement.