Dimensionamiento del Sistema Fotovoltaico

The effect of additional road use

A topical issue is the effect that additional vehicles have on the incidence and severity of road crashes. Intuitively it would seem that the likelihood of any vehicle being involved in a road crash increases with each additional vehicle on the road. As such, it would appear that the marginal (i.e. additional) cost of road-use would be much higher than the average cost and that the external costs of any road-use are greater. Thus from the point of view of road crashes, other drivers are better off the less roads are used.

The size of this effect is debatable. More congested traffic can prompt people to drive more slowly and carefully. While this reflects costs to those road users, the effect can be to lower the incidence and severity of road crashes. Greater road use can also motivate and fund greater investment in infrastructure, which can both improve road safety and driving pleasure. Thus the net effect on road crash costs is not clear.30

30

See Martin (2005) or Parry et al. (2007) for further discussion on this topic and links to further work.

The problem of vehicle size

The effect of additional road use is clearer when it applies to heavy vehicles. When it comes to road crashes, size matters. The severity of an accident is closely linked to the relative size of the vehicles involved. In a two vehicle collision, the occupants of the smaller vehicle are far more likely to be killed or seriously injured than in the larger vehicle. This is the case for standard passenger cars involved in collisions with heavier sports utility vehicles (SUVs) and for all passenger vehicles involved in accidents with trucks and buses.

A key implication of the importance of relative size is that by their mere presence, heavy vehicles impose external costs for other road users. These costs include the additional severity of accidents, the additional discomfort to drivers of light vehicles and

distortions in people’s choice of vehicle and road use. Simply put, people are better off driving on roads surrounded by lighter vehicles.

The concern about relative size of passenger vehicles has increased in recent years (particularly in the US) due to the increased prevalence of SUVs and even heavier vehicles such as Hummers. It wasn’t clear at first whether increased passenger vehicle size was necessarily bad for vehicle safety. Intuitively it would seem that if everyone used larger vehicles then we might even be safer. However, not everyone chooses to drive the larger cars and so large disparities in vehicle size exist. Furthermore, there are additional reasons to be concerned with vehicle size.

Firstly, pedestrians, motor cyclists and cyclists suffer as a result of larger vehicles. All of these parties are more likely to be killed or injured if hit by a larger vehicle.

Secondly, there is some evidence that the driving behaviour of passenger vehicles changes for the worse with larger vehicles. Recent US evidence31 suggests drivers of heavier passenger vehicles are more likely to be involved in a crash and drivers of equal sized vehicles are more likely to be killed or seriously injured when the vehicles are larger.

There is an additional problem of relative size. The presence of larger vehicles

encourages consumers, in the interests of their own safety, to themselves purchase larger vehicles. This effect has been described as an ‘arms race’ for larger vehicles which results in increased private spending on larger vehicles and running costs and greater social costs associated with emissions and congestion. Both these additional private costs and public costs are external costs associated with the presence of large vehicles on the road.

31

The issue of relative vehicle size is also gaining greater recognition with regard to road freight policies.32 While trucks are under-represented (on a distance travelled basis) in terms of road crashes, they are over represented in terms of road-fatalities and serious injuries.33 The problem of relative size means that regardless of fault, all else being equal, more trucks on the roads increases the risks to other road users.

It should be possible to make reasonable estimates of the relative size externality associated with a large vehicle such as a truck or SUV. Given available data on the accident rates and fatalities by vehicle types it is possible to estimate the impact of replacing large vehicles with smaller vehicles or other forms of transport. Using such an analysis, White (2004) estimated that the safety benefits of replacing a million SUVs with smaller cars in the US were between US$242 (≈$A330) and US$652 (≈$A890) per replaced vehicle per year.34

In addition to the increased accident externality, the external costs include the increased discomfort for road users and the ‘arms race’ effect. An indication of the former could potentially be obtained through stated preference surveys. Estimating the latter, would require an estimate of how consumer choice of vehicle size changes in response to the presence of other vehicles.

The ‘relative vehicle size’ effect has now been accepted as an issue. Available research suggests that it is sizeable and at least some of its effects quantifiable. Clearly

quantification of the relative size effect could lead to changes in estimates of the external costs associated with heavy vehicles and road crashes.

5 Conclusion

This paper supports the case that the cost of road crashes is much more significant than is commonly reported, both in terms of overall costs and the extent to which these costs are internalised. The key issues raised in this paper are not new. They have generally been accepted by experts in the field, but largely have not made their way into effective analysis of policy.

32

BTRE (2006) recognise this. They state ‘… regardless of issues of cause and fault, it is reasonable to argue that heavy vehicles impose an external cost on other road users.’

33

See BTRE (2006), pp. 18-19.

34

The author also estimates that for every fatal crash that individuals avoid by driving larger vehicles ‘at least 4.3 additional fatal crashes involving others occur’.

The recent BITRE study reported that its headline estimate of the road crash costs in Australia in 2006 of $17.85 billion (2006 dollars) was conservative, as it was obtained using a human capital approach to valuing the most significant human component of costs. The alternative approach based on the WTP approach should be adopted. This is the approach that is supported by the vast majority of experts and comparable

Government agencies around the world.

There should be no debate as to which method should be used for public policy analysis. The human capital approach (or at least how it is applied) because of what it excludes, underestimates the social costs of road crashes. In addition, it is not as theoretically sound as is the WTP approach. The debate between using the WTP method or the human capital method is more about whether it is better to be broadly right or more precisely too low.

Recent Australian research suggest a value of a statistical life (VSL) to a private

individual in the order of $6 million (2006 dollars) is appropriate for general application. An upwards adjustment to this amount is also appropriate to reflect the value friends and relatives place on an individual’s life. Furthermore a relatively high VSL may be

justified for road crashes, given the age profile of those killed and injured.

Adoption of the WTP approach is particularly significant for the analysis of internal and external costs. The increase in cost estimates reflect loss in life and quality of life, much of which are borne by road-users not at fault and by friends and relatives of victims. As discussed in this paper, the problem of over-confidence of drivers means even less of the true cost of road crashes is effectively internalised by drivers.

The problem of vehicle size is an increasingly important issue that demands further attention. Although the issue has been recognised, there has been little research that has attempted to quantify the effects in a way that may support using them in policy analysis.

A large revision to the external cost of road crashes and greater consideration of the other factors discussed would have important implications for cost-benefit analysis of transport policy. It is worth recognising the concern by some that an increase in the external costs of road crashes could drive inefficient investment and regulation. Properly applied this should not be the case, but regardless, rigour and caution should be applied in further policy analysis in this area.

In summary, the key conclusions from this review are:

• The significance of road crash costs in Australia has been consistently

underestimated, both in terms of the overall cost and the extent to which these costs are incorporated (i.e. internalised) in road-users’ decisions.

• Based on recent research, the total road crash costs in Australia are more than what has been commonly reported. This increase relates to costs of loss of life and quality of life, much of which is not borne by the road-users responsible.

• The value of risk to life is a key issue. For policy analysis in all transport modes, values used should reflect the WTP-based approach rather than the human-capital approach that undervalues life. The WTP-based approach is now common practice in other areas and other developed countries.

• The impact on friends and family should be further investigated and should be considered in policy analysis.

• Greater consideration should also be given to the problem of (passenger and freight) vehicle size and the external costs that larger vehicles impose on other road users.

• Overconfidence causes road-users to not fully internalise the costs to themselves as they underestimate their likelihood of being involved in a road crash.

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