Attribution Methodologies for Mobility Impacts
Natalia Kotelnikova, Université Paris Est, Laboratoire Ville Mobilité Transport, Marne-la-Vallée, France, Fabien Leurent, Université Paris Est, Laboratoire Ville Mobilité Transport, Marne-la-Vallée, France, Alexis
The paper provides an analytical framework, evaluation schemes and guidelines to impute or attribute mobility impacts to either trips, trip-makers, origin-destination pairs, zones, all as emitters or receivers
Transportation modes involving motorized vehicles, from the car to the plane passing by the bus and the train, all consume energy and emit local pollutants – chemical and noise. Even electric vehicles emit fine particles of matter. Furthermore, it frequently happens that vehicle traffic is plagued with congestion, which is another kind of impact caused by some emitters onto some receivers.
A number of methods have been proposed to evaluate such or such kind of impact and to relate it to specific emitters and / or receivers. In environmental evaluation, such linking from impacts to contributors is called “attribution”. In economic analysis it is better known as “imputation”. The purpose behind attribution and imputation is to identify the causes of impacts and to design specific management schemes to curb the negative kinds of impacts. A related purpose is to evaluate the impacts on monetary grounds and to devise compensation schemes, possibly including pricing schemes to harvest revenues and redistribute them to compensate receivers for hindrance.
The paper puts forward an analytical framework to devise attribution schemes for mobility impacts in a territorial area. The framework applies to every mode of ground transportation. The cornerstone is to evaluate the local impacts of a given vehicle on every stretch of road- or railway, together with the number of passengers in the vehicle. Thus the individual contributions to local impacts can be identified. By kind of impact, such individual contributions can then be aggregated along any path sequence, hence for any individual troip from origin to destination. The attribution scheme may pertain to the individual trip-maker. Alternatively, impacts can be attributed to the building that contains the activity generating the trip, or to the zone that contains that building. Furthermore, some averaging operations at the building or zone level can yield object attributes useful to aid decision-making in urban plans – such as location decisions for dwellings and activity settlements.
The paper is organized in seven parts. Part 1 gives a general introduction. Part 2 provides a bibliographical review of attribution methods in the fields of environmental evaluation and economic analysis: it deals with the concepts of “functional units” (used in LifeCycle Assessment) and “marginal costs” caused by “marginal users”. Then, Part 3 provides the framework: a series of attribution schemes are composed and discussed. Part 4 deals with the associated computation scheme that may be implemented: travel demand models especially for traffic network assignment, together with environmental models of pollutant emissions and energy consumptions are useful there. Part 5 is devoted to an application instance of urban transportation in the greater Paris area at the level of individual trips, then of origin-destination pairs, next of zones either as emitters or receivers of given kinds of impacts. To conclude, Part 6 provides a synthesis and points to some topics for further research.
Association for European Transport