Environmental Engineering Reference
In-Depth Information
6 A Note on UMM Estimation
The purpose of the UMM module is to estimate the transport flows essentially
corresponding to goods and raw materials for public and building works, and the
vehicle flows generated by waste management and urban network maintenance
(sewers, water, phone) and removals (Routhier and Toilier
2007
). These flows
represent about 10 % of UGM road occupancies but have different natures and
temporal distributions. They are composed of a heterogeneous set of flows:
• Transport flows induced by building and infrastructure construction.
• Waste management trips.
• Physical logistics flows for urban network development and maintenance (water,
electricity, gas, telecommunication)
• Trips related to personal and professional removals.
• Trips related to community needs like schools, hospitals and postal services
(excluding parcel and express deliveries, already included in IEM movements).
Due to the heterogeneity of these categories it is not always easy to find a
significant set of data to model them. Indeed, although the two last categories are
more or less homogeneous or easily identifiable with a group of homogeneous sub-
categories, the other three represent a wide variety of organizations and practices
which are not always easy to identify and represent in a model. Consequently,
UMM estimation is done using different and mostly partial sources (Ségalou et al.
2004
), on the basis of specific studies that do not necessarily take into account the
spatial context and the seasonal characteristics of certain flows (seasonal variation
is often common for construction flows and other flows such as community needs
and the waste management trips). The method proposed is therefore an overall
estimation of road occupancy values (in km.PCU) in the flows concerned. Taking
into account their relative distribution (Toilier et al.
2005
), priority is given to the
estimation of the two first categories of flows (in terms of data quantity and quality
and estimation robustness).
Since most surveys do not clearly identify UMM flows, as they are often
regarded as negligible and fluctuating in time or space (they are not subject to
thorough surveys, according to Albergel et al.
2005
), the method aims at gener-
ating weekly road occupancy values from annual estimations based on rough ratios
(Table
6
). Concerning construction flows, the annual mean travel distances depend
on the size of the city and the location of dumps, quarries and cement works. The
location of these flows is, however, not well known. That is why they are assigned
only as flows generated by deliveries and pick-ups. The remaining flows are
directly related to the urban population. The main sources for estimating the road
occupancy for each category and defining the ratios (Ségalou et al.
2006
) are
presented in Table
6
. It is noteworthy that such ratios are first presented in terms of
Km per inhabitant and year then the percentage of heavy vehicles providing such
transport (in distances travelled) is reported. For example, for construction,
12.1 km are generated per vehicle and year, of which 9.8 (81 %) was travelled by
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