Abstract:
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While absolute accessibility of a region is important, comparison of accessibility across time and regions is
more interesting in understanding transport system change. This master thesis tries to find the proper
accessibility measure that enables that analysis. The work will have to adapt to the resources available
that are somehow limited by the broad scope of the study. From that the proper measures could be
defined.
As an application of the research above aforementioned the present thesis analyses the change in private
car traffic accessibility in two different ways:
1. The losses in accessibility in private car traffic in Switzerland due to a virtual removal of freeways to
reflect network sizes in 1950, 1960, 1970, 1980 and 1990.
2. The development of accessibility in private car traffic for the complete road network of the canton
Graubünden from 1950 through 2000 in 10 years steps.
In order to calculate accessibility, isochronic and gravity mode approaches are the ones used after an
evaluation of the available data. On one side, the number of activity points reachable in a given time (i.e. 1
or 2 hours) is determined, with an isochrone defined as a set of points with the same travel time from a
given place.
Alternatively, a gravity measure is used to calculate accessibility by means of a potential function. To
establish the possible activity or opportunity locations, the community-level population data are used. A
data base is implemented for every decade. In determining travel time, an assignment model is
implemented to calculate the time-effort (which is defined as the travel cost) required for passenger trips
by car with a travel time matrix for the approximate 3000 municipalities. That is managed with the help of a
traffic software (VISSUM). The level of service of the road network, from which the travel time between
different nodes is established, is calculated considering permitted speeds and capacities trough the time.
Those data come from the revision in old publications and manuals. Finally, accessibility is calculated as
the travel time weighted sums of opportunities by means of a statistical program that allows programming
and a good manage of large databases (SAS). The results from these calculations are hard to visualize. In
order to manage that, Arch View software is used
The analyses of the results will give indications as to which areas benefited from the improvements of the
road network and how the distribution of accessibility for all municipalities has changed over time. |