Detailed cost-benefit analysis of potential impairment countermeasures

Research in the framework of the European research programme IMMORTAL

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Vlakveld, W.; Wesemann, P.; Devillers, E.; Elvik, R.; Veisten, K. (2005). Detailed cost-benefit analysis of potential impairment countermeasures; Deliverable D-P2 of the IMMORTAL project. European Commission, Brussels.


Vlakveld, Willem; Wesemann, Paul; Devillers, Eline; Elvik (TØI), Rune; Veisten (TØI), Knut




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Introduction Traffic accidents in Europe as in other parts of the world are an enormous problem. In general road safety can be improved by measures regarding infrastructure, vehicle, or behaviour. The behaviour of the driver is influenced by his competences and capabilities. These competences and capabilities are the basis for the IMMORTAL research programme in which impairments (chronic and acute) and their influence on traffic safety are determined. In order to decide on possible policies for impairment countermeasures it is necessary to have an insight in the socio-economic effects of the policies. This is provided in this report by means of a cost-benefit analysis. A socio-economic cost-benefit analysis provides an unambiguous appraisal method, which takes into account all relevant social effects. Efficiency assessment In this report we use a cost-benefit analysis to assess the potential impairment countermeasures. Another method for efficiency assessment is the cost-effectiveness analysis. Both methods have a common point of departure, namely the project-effects matrix (the overview of costs and effects). In a cost-benefit analysis the advantages and disadvantages are expressed in terms of costs and benefits and are wherever possible expressed in monetary terms. All effects are taken into account, both intended effects and side effects, including effects for those not directly involved. The main difference is that in the cost-effectiveness analysis, only the intended effects are included (in this case safety effects) and only the costs to obtain these effects are expressed in monetary terms. This type of analysis proves to be valuable for cases in which the effects have to be maximized within a given budget or the costs have to be minimized guaranteeing a certain level of effect. However in order to make policy decisions it is necessary to have insight in all relevant social effects, not just the intended ones. Impairment factors In Deliverable R1.1 within the IMMORTAL programme, a review of relevant epidemiological studies has been made in order to evaluate the effects of various impairments. In a meta-analysis the studies were summarized leading to estimates of the relative risks associated with various impairments. If the value of the relative risk ratio is larger than one, the impairment leads to an increased risk of accident involvement. The higher the relative risk ratio is, the larger the contribution of a certain risk factor to accident involvement of the impaired drivers. Values below one indicate that the impairment leads to a reduction of the risk of accident involvement. This could be caused by behavioural adaptation. If for instance a driver is aware of his eyesight deficiencies he might avoid difficult circumstances such as driving at night or with reduced headway distances. The results from the meta-analysis show that most medical impairments only have a small effect on the accident involvement. The estimates of the relative risk ratios associated with the impairments are in most cases in the range between 0.8 and 2.0. The estimates are in no case greater than 6. Hence, the effect on accident involvement of the different impairments tends to be smaller than the difference in accident involvement normally found between an 18-year old driver and a middle-aged driver. However, there are some limitations to the use of epidemiological data. In this report, most of the epidemiological evidence is taken as a basis for doing the cost-benefit analysis, but evidence that is weak (from just a few studies or from studies without a rigorous design) is not included. Policy options A driver has to perform certain tasks in order to reach his destination safely. Whether he/she is able to meet the task demand depends on his competences and capabilities. These are influenced by respectively chronic and acute impairments. The directions for policy options to control impairments can be based on these three elements: - lowering task demands by vehicle adaptations or driving licence restrictions (no driving in the dark etc); - improvement of competences by medical treatment, psychological rehabilitation or training; - withdrawing drivers with low competences; selection based on tests or on self-selection; - improvement of capabilities; deter drivers not to impair themselves, use of warning systems (such as fatigue warning systems). In order to perform a cost-benefit analysis a concrete countermeasure for specific impairments needs to be defined. From all possible policy measures for all possible impairments a selection is made. This selection is made based on 1) the increase in accident risk of the impairment, 2) the prevalence of the impairment, 3) the effectiveness of the countermeasure and 4) the political and public support for the countermeasure. This has led to the following selection of countermeasures that have been assessed for four countries on the North, South, East, and West boundaries of Europe (Norway, the Netherlands, Spain and the Czech Republic): - mandatory eyesight testing (three specific types of tests); - increasing random road side breath tests (combined with a zero BAC limit for young drivers); - installation of alcohol lock for drivers with an alcohol problem. Because the cost-benefit analyses in this report are only carried out for the four mentioned countries, the results are not representative for Europe. In fact there is no 'European average' for a certain countermeasure. Even between neighbouring countries that have many political and cultural aspects in common, due to minor differences between the two legal systems in those countries, the outcome of a cost-benefit analysis for a particular countermeasure may differ considerably. The four countries were chosen for practical reasons (all within the IMMORTAL-consortium and therefore fast access to data sources) and heterogeneity (different parts of Europe). Cost-benefit analysis As mentioned, in a cost-benefit analysis the relevant impacts of the countermeasure must be identified and expressed in monetary terms. The impacts that are assessed in the cost-benefit analysis of impairment countermeasures are: -changes in number of road accidents. The change is determined by using the relative risk ratio to estimate the number of attributable accidents for a specific impairment. The reduction of these attributable accidents depends on the type of countermeasure (when a driving licence is withdrawn and compliance is 100% (which is off course questionable), all attributable risks are gone). In case of treatment we have assumed that the treatment is 100% successful, leading to a normal relative risk ratio of one. The valuation of the safety effects is based on the social costs of accidents in a country divided by the annual traffic fatalities. This method is described by the European Commission and is sometimes called the One Million Euro Test . - changes in amount and type of mobility. When a driving licence is withdrawn, the car driver is forced to either stop travelling or use another mode of transport, assuming all drivers comply with the withdrawal of the driving licence. For both the loss of trips and the shift of trips to other modes of transport, the loss of benefits is valued. The cost-difference method is used for the generalized costs (time costs and variable vehicle costs), assuming a common demand function for all transport modes. The effects are different for private drivers and commercial drivers. This difference is taken into account. Also, a shift in use of transport modes may lead to an increase of accidents in those ‘new’ transport modes. This second order safety effect is also determined and is in some cases rather substantial. - changes in environmental effects. The change in amount and type of mobility also leads to environmental effects. The reduction in environmental effects due to the decrease of car driving (first order effect) has to be corrected for the change of environmental effects due to the increase of other modes after the modal shift (second order effect). - costs of countermeasure. All related project costs during the introduction period and operational period are taken into account, regardless of who is paying the costs. Results of analyses for countermeasures The results of the analyses are benefits and costs, expressed in million euros. The socio-economic yield is expressed in terms of the benefit/cost-ratio. If this ratio is larger than one it means that the social benefits are larger than the costs. When the benefits are negative, this ratio will be negative as well (and therefore smaller than one). The annual effects are expected to remain the same over the project period, thus mathematically the benefit-cost ratio will not be influenced by the chosen time period. Eyesight testing The socio-economic yield of mandatory eyesight testing is in general negative. This is mainly caused by the loss of welfare due to the withdrawal of the driving licence. Especially when the driving licence is withdrawn at a relatively young age, the mobility effects may have a large negative impact. Besides the large negative mobility effects, the traffic safety benefits are small, due to the rather small relative risk ratios and the rather large negative second order safety effects. The negative second order safety effects depend on the modal shift to other modes of transport. Sometimes these new modes have an even higher risk ratio than the impaired car driving (for instance mopeds). The first order safety effect due to the decrease of impaired car drivers is thus partly undone by the second order safety effects due to the increase on other modes of transport. The only eyesight test that might lead to positive results is the reduced field of view test. This eyesight impairment leads to considerable relative risk ratios, the car drivers that suffer from this impairment are older and therefore the mobility effects of withdrawing the driving licence will be less decisive. The disadvantage of the UFOV test is that the data regarding prevalence and effectiveness is not completely reliable. Most epidemiological studies stem from the same source, which is not completely independent. This makes the UFOV test, at this moment, less qualified as a decisive test for acquiring a driving licence. The sensitivity and selectivity of the test is, compared to other medical tests, acceptable but there is also a risk to include false positives and exclude false negatives. In general, the withdrawing of driving licence leads to large negative socio-economic effects, especially when the driving licence is withdrawn at a young age. It seems thus more promising to focus on various treatments rather than on driving licence regulations. Alcohol related measures Three countermeasures for drunk driving have been assessed, namely increased roadside breath testing, a zero BAC limit for young drivers, and the installation of an alcohol lock. All measures seem promising. This is mainly due to the fact that the countermeasures aim at preventing drinking and driving by means of deterrence. In principle these countermeasures will not cause any mobility effects and thus also no second order safety effects. Although in principle the measures do not prevent driving (only drunk driving), it may be possible that drivers rather prefer to drink and not to drive than to drive and not to drink. This mobility effect is only accounted for in the Norwegian cost-benefit analysis on zero BAC limit for young drivers. The Czech Republic already has a zero BAC limit for all drivers. In the Czech Republic the data regarding drunk driving and the accidents related to this drunk driving are rather poor. For instance, statistics show that the percentage of road fatalities caused by drunk drivers is 8% as opposed to about 30% in the Netherlands. Despite the fact that this country seems to suffer from underreporting (and the effects are thus underestimated), the effects seem promising. Only for Spain the costs for alcohol-lock are slightly higher than the benefits. It seems likely that this negative effect for Spain is caused by the assumptions that had to be made due to lack of input data. General conclusions and recommendations The title of the report is Detailed cost-benefit analysis of potential impairment countermeasures. The word 'detailed' in the title is somewhat misleading. The presented cost-benefit analyses are detailed in the sense that as much as possible all the effects of the measures are taken into account, but the word 'detailed' in this case doesn't imply preciseness. Cost-benefit analysis is a rather complex instrument and the results depend heavily on the quality of the input. Some input, especially regarding the different aspects of traffic safety, is missing or is rather speculative. Therefore it is necessary to make assumptions. The assumptions made in this study however will probably not change the general conclusion, namely that withdrawing driving licence (especially at a young age) based on mandatory eyesight testing will push towards a negative socio-economic yield. Preventing drunk driving through random road side tests and installing an alcohol lock all seem promising, although the prevalence of alcohol abuse and the contribution to the road fatalities seems to be underreported especially in the Czech Republic. The cost-benefit analysis provides objective information for policy makers by presenting an overview of all relevant socio-economic effects in a structured manner. It has a normative foundation, based on aggregating individual/household preferences, but the choice for policy measures always remains a political choice that might be influenced by other factors than the socio-economic yield. However some policy recommendations are included: - treatment of eyesight problems. The withdrawing of driving licences leads to large negative socio-economic effects. The countermeasures for eyesight problems will lead to a more positive socio-economic yield if they are based on treatment rather than driving restrictions. An additional advantage is that this will not prevent people from seeking medical treatment. What has to be kept in mind is that the threat of loosing one's driving license (due to driving restrictions) may lead to medical treatment if medical treatment is possible. In order to meet the criteria for visual acuity, drivers will buy (better) glasses before they do the eyesight test. - research on UFOV testing. Despite the substantial safety gain for UFOV testing, it leads to a negative net benefit in Norway and the Netherlands. This is mainly caused by the high costs related to loss of mobility in Norway and the Netherlands. As these costs are lower in Spain, the net benefit is positive for this country. A small change in the valuation of mobility loss will probably lead to a positive net benefit on UFOV testing in Norway and the Netherlands as well. This makes UFOV-testing promising. However, the quality of the input data is (partly) questionable. This leads to the conclusion that the UFOV test is not ready to play a decisive role in the provision of driving licences and more research is needed to determine prevalence, relative risk ratios, and effectiveness. - deregulation of license restrictions. Based on this analysis it is clear that permanent withdrawal of driving licences leads to large negative socio-economic impacts. Especially when the initial relative risk ratio of the impairment is not so high and the drivers are relatively young (under 65 years old). Therefore it might be fruitful, based on socio-economic principles, to review existing regulations. - assessment of more countermeasures. The number of possible countermeasures is infinite and although explicit criteria were used for the pre-selection, it is possible that more promising countermeasures will be ‘invented’ or even are already in place in a particular country. - stricter regulations for registration of accidents. One of the largest difficulties in this study was the lack of accurate and detailed information. The European Commission might provide a framework for registering accident data and perhaps even medical information.

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SWOV, Leidschendam