Monetizing Harmful Road Traffic Emissions

Air pollution kills 2.9 million people a year. It is now the fourth major cause of premature deaths [1].

Road traffic is a source of significant harmful emissions: carbon monoxide, carbon dioxide, nitrogen dioxide, sulphur oxides, hydrocarbons and fine particulate matter, which have a dramatic impact on people’s health and well-being, on natural ecosystems, and on agriculture and infrastructure. More than 50% of particulate matter emissions in urban areas are traffic-related, displacing emissions from industry, commerce and home heating combined. In addition, the United Nations has estimated that more than 600 million people are exposed to hazardous levels of pollution generated solely by road traffic [4] with 87% of the world’s population exposed to this type of pollution [1].

What course of action can road administrations take to reduce traffic-related emissions?

Pavement characteristics, such as type of material, surface roughness, geometry and maintenance have an effect on the amount and severity of harmful emissions from vehicles using the roadway [2], [3], [5] and [6]. However, the choice of an intervention strategy is primarily based on cost, with environmental and health impacts mostly considered to be intangible. This is why road authorities do not take them into account when deciding on the type of intervention in repairing a degraded road.

Figure 1 A damaged road

The solution could be to attribute a cost to environmental impacts in a way that would make it possible to estimate their economic weight and integrate them into road management systems.

The HDM-4 software program, recommended by the World Road Association, is used for road surface behaviour predictions and economic evaluations in road design and maintenance. Using data collected from an existing road network, the program simulates several roadways and intervention strategies suggested by road experts. It is the only widely used software that calculates emissions in terms of tons per year, types of pollutants and intervention strategies.

Parameters that vary from one intervention option to another are asphalt quality for the new surface layer and maintenance frequency. These intervention programs will be compared to a strategy 0, which consists in leaving the roadway in its original state or, in other words, no intervention.

Recent epidemiological and economic researches suggest coefficients in dollars per ton, representing the cost of the impacts of each type of emission. Multiplying the HDM-4 quantities by this coefficient attributes an environmental cost to each type of intervention.

Figure 2 Cumulative emission costs for each option over the entire analysis period for one intervention scenario.

To summarize the results, only the three strategic extremes were selected:

• A strategy (2) of complete roadway levelling and regular maintenance;
• A strategy using cheaper materials and no maintenance (7);
• A strategy (0) which consists in leaving the road in its initial state with no intervention.

Figure 3 Cumulative emission costs for each option over the entire analysis period for one intervention scenario.

Regardless of the strategy, intervention reduces the environmental impact by more than a million dollars. Intervention represents an additional savings of $200,000 for society in environmental costs for this project alone—and only seven kilometres of road were modelled here.

In conclusion, road surface managers have the means to reduce the environmental impacts of road traffic. Additionally, the environmental benefits can translate into several million dollars. It is therefore recommended to attribute a cost to environmental impacts so that they are integrated into management models along with other costs. Taking these impacts into account in road surface management should result in a more sustainable management of road infrastructure that will benefit all of society.