University of California Transportation Center

Particles and gases in the atmosphere scatter and absorb light, and thereby reduce visibility (Watson and Chow, 1994; Richards et al., 1990; Ozkaynak et al., 1985). Although natural sources of particles, such as volcanoes, can significantly degrade visibility, it generally is true that “when visibility is poor...most particles are found to be of human origin, from sources such as power plants, vehicle exhaust, biomass burning, suspended dust, and industrial activities” (Watson and Chow, 1994, p.244). Poor visibility diminishes the enjoyment of scenic vistas and makes travel hazardous1. Statistical analyses of property values (discussed below) reveal that people are willing to pay extra for houses in areas with good visibility and air quality.

The particles that are most efficient at scattering light are roughly the same size as the wavelength of visible light -- about 0.5 µm (Watson and Chow, 1994; Richards et al., 1990; Ozkaynak et al., 1985). Because most particles emitted by the combustion of diesel fuel, and some particles of re-entrained road dust, are 0.5 µm ± 0.4 µm, emissions related to motor-vehicle use can significantly degrade visibility. In support of this, Trijonis (1984) has estimated that direct emissions from heavy-duty diesel vehicles in California cause 10% to 20% of the light extinction.

In this report, we review some of the literature on the cost of visibility, and then develop our own estimate of the cost. For our own estimate, we select a simple hedonic model, from the meta-analysis of Smith and Huang (1995), of the relationship between the asset value of homes, levels of total suspended particulate matter (TSP), and per- capita income. Because the hedonic price of TSP undoubtedly comprises the price of visibility (as well as the price of other effects of TSP, such as bad health), and because we can relate TSP emissions to visibility, we can use this hedonic model to estimate the visibility cost of TSP emissions. Specifically, we will apply this hedonic meta-model to estimate the visibility cost of all anthropogenic TSP pollution, and of motor-vehicle TSP pollution, in every county in the U. S. in 1990.