Impact analysis: transport
- The text on this page is taken from an equivalent page of the IEHIAS-project.
As part of the EU-funded INTARESE project, which contributed to the development of this Toolbox, a series of case studies was done, in cities across Europe, to assess the health impacts of different transport policies.
In the Hague, health effects deriving from air pollution, noise, traffic accidents and changes in physical activity were assessed. Health outcomes included life expectancy, hospital admission for cardiovascular and respiratory disease, sleep disturbance, annoyance by traffic noise, myocardial infarction and serious traffic accidents. Because of this wide range of outcomes, some form of aggregation was clearly essential. Two approaches were used - one to derive health-based measures of impact, and the other through a detailed monetary valuation.tary terms.
Health-based measures
A number of different health-based measures were calculated for the various outcomes, including attributable numbers deaths or hospital admissions, life years gained, and the number of disability-adjusted life years (DALYs). The first two of these are clearly limited because they make no allowance for the timing of death or the severity or duration of morbidity. Life years gained is more informative in this respect (for it takes account of the age of death) but is restricted to mortality. (Life years gained, itr should be noted, was used instead of the more common ‘number of attributable avoided deaths’ because positive indicators such as this are considered to provide a more effective basis for communicating information about common environmental, occupational and lifestyle risk factors.) The DALY includes morbidity, and thus is more comprehensive, but suffers from two constraints: it is less easy to communicate and it provides only a relative measure. It is mainly suitable, therefore, to compare effects of different stressors.
Monetary valuation
The use of money (Euros) as the measure of impacts indicator has several advantages. Firstly, it is easy to communicate; secondly, it allows for an easy comparison between costs and benefits from implementation of the policy; and, thirdly, it enables direct comparison between different policy measures. The main disadvantage is methodological, in that not all costs involved can easily be quantified nor monetised.
In this case, monetary assessment was limited to the environmental and health effects of changes in air pollution, noise and traffic accidents. Other benefits, such as reduced congestion, were not included. The estimated monetary benefits cannot, therefore, be directly compared with the costs of policy implementation (e.g. to derive a measure of cost effectiveness). Equity issues were considered by modelling the distribution of exposure by socio-economic status, but the potential impact on the distribution of health effects was not assessed.
Results
Results of the analysis showed some of the dangers inherent in impact analysis, and the importance of care both in selecting which outcomes to include in the analysis and which measures to use. The effects of the traffic circulation plan on the number of people dying because of noise, for example, is zero. When using life years lost as the impact indicator, therefore, the contribution of noise to the total burden of disease is likewise zero; air pollution and traffic accidents account for the full impact. On the other hand, noise is an important source of annoyance and reduced quality of life, which both DALYs and monetary valuation take into account. These nevertheless differ in the weights attached to these effects: when measured in terms of DALYs, noise was responsible for 15% of the total burden of disease; in monetary terms it was seen to be the main contributor to the total health costs.