Strategic Multimodal
transport models packages can be used for a variety of purposes: 1) to forecast
the overall demand for travel at some specified date in the future, given
predicted changes in factors external to the transport system, such as
population, employment and household income; 2) to allocate forecast demands
for travel to the various modes of transport and, within each mode, to
individual roads and public transport services; 3) to calculate the levels of
service offered by each mode; 4) to provide information on vehicle and
passenger flows and travel costs necessary for operational, environmental,
economic and financial appraisals.
On the basis of the
purpose above, the strategic models may be synthetically aggregated in the
following main functional categories:
·
Data processing;
·
Network assignment;
·
Project management;
·
Site analysis.
Typical application
phases for these models are the investigation on transport demand and the
operation of multimodal transport systems within urban or regional
transportation planning and feasibility studies of new infrastructure, network
upgrading, global operational measures application.
Typical outputs are
graphic and numerical network and flows representation, flows assignment, isochronic lines calculation and mapping, emission
calculation.
The disadvantage of strategic
models for emissions modelling is that there is often a need to compromise in
term of spatial details. Zones are generally quite large and networks
relatively coarse. Also, vehicle emissions output can normally only be
calculated from average link speeds, whilst actual vehicle emissions depend on
actual driving patterns (e.g. acceleration/deceleration, stops/starts). As a
consequence they are not suited to evaluating the effects of traffic management
measures and small scale schemes, and all the measures triggering changes in
vehicles speed cycle.
|