Using DALYs to Assess the Impact of Transport Measures on the Dutch Disease Burden

Abstract

ISEE-234 Objective: Potential health effects of transport range from noise annoyance to injury to mortality. To compare and evaluate different transport policy options, there is a need to express these health effects in a comparable way. One of the most common methods to do this is the calculation of disability adjusted life years (DALYs), which express the number of people with a certain condition and the severity and duration of that condition in one single number. However, the outcomes of DALY calculations are often relatively uncertain, mainly due to variation in the various input factors. This can make it hard to interpret the outcomes of DALYs and to value their use, especially in more local (more uncertain) assessments. The aim was to quantify effects of speed limit reduction on highways at 9 locations in the Netherlands on health impacts related to air pollution, noise, and traffic safety. We have tried to evaluate the use of DALYs for these types of intervention studies. Material and Methods: DALYs calculations using exposure distributions, exposure-effect data, disease prevalence, and demographics. Results: It appears that the expected health benefits of speed limit reduction are small, except for the effect on traffic safety. We estimate that the disease burden attributable to road traffic noise and traffic-related air pollution decreases by 4% and 2%, respectively. The disease burden due to traffic safety decreases by around 59%. Conclusions: Because a lot of choices and assumptions have been made and the variation caused by uncertainty in the input variables is substantial, results from local impact assessments must be interpreted with caution. DALYs can be useful to support environmental health assessments and decision making, but should not be used as a sole basis for policy making.