Estimated Data Production for Urban Goods Transport Diagnosis - Sustainable Urban Logistics: Concepts, Methods and Information Systems - page 116

3.1 Observation and Modelling Unit

The question is how is it possible to build a database capable of solving the
problem of the road occupancy. Current surveys such as the French ''Transport
routier de marchandises'' (TRM) surveys describe the use of a stratified set of
vehicles throughout the country. However, since no organization is described, it
does not address the city or make it possible to answer the question of road
occupancy (Which vehicles? Which activities? Which organization? How many
kilometres?). Another unit usually taken into account is the commodity. It is
generally used in optimization models for transport companies but it does not
allow capturing the urban specificity of the organization deployed at urban scale
(Gonzalez-Feliu and Routhier 2012 ). It was therefore necessary to build specific
surveys, in order to answer the main stakes above, as was done for the description
of individual mobility.
The statistical unit observed in individual mobility surveys is the trip associated
with a reason for going to a destination. In a sample of households, the description
of the set of trips made by each individual of a household in a day makes it
possible to build the total number of trips in a city. What is the relevant obser-
vation unit for urban goods movement surveys? The deliveries and pick-up
operations carried out by one vehicle was chosen (Bonnafous 2001 ). If all the
operations (deliveries and pick-ups) in a week for a stratified sample of estab-
lishments (the premises belonging to each firm) are characterized accurately, it is
possible to evaluate, by extension, the total deliveries and pick-ups carried out in
the city. Furthermore, as for each operation, it is possible to observe the organi-
zation of the transport (by orienting the survey to the drivers) (Fig. 1 ).

: at this place it is possible to observe the formation of vehicle flows and their impact on the
urban environment according to:
- the transport system,

- the logistics strategy of the company,

- the environment of the establishment.

Fig. 1 A statistical unit for solving the issue