VISEM
- VISEM Screenshot
VISEM is a Transport Information System - Generation Model.
The key features of the demand model VISEM display activities and their link to a "mobility program". This model distinguishes between several homogeneous behavioural population groups and generates a specific set of activity chains for each of them.
You can also create future scenarios using VISEM. The availability of diverse forms of transportation, group membership, activity chains and other parameters required for the specific decision-making situation are taken into account.
Travel demand modelling with VISEM
Knowing the transport demand within the area to be analysed is essential for planning and analysing transport networks. For travel demand calculations VISEM performs the following three steps :
- Trip generation (calculation of originating travel demand),
- Trip distribution (specification of destinations) and
- Transport mode choice.
These three logic units are not processed separately or successively, but are interconnected. Two essential VISEM concepts are applied to these three steps: Calculations are based on homogeneous behavioural population groups and on activity chains. Project management is VISEM's outstanding feature. The clear tree structure allows the user to access all project data and provides easy data management.
It is possible to efficiently create travel demand data in the form of trip matrices based on model data and calculations generated with VISEM. VISEM output data is directly used by VISUM. An assignment procedure allows the data to be assigned to the new traffic network (service data). On the one hand, results can be displayed and analysed in VISUM and on the other hand, they can be exported to be integrated into VISEM's project data. Even interactive matrix processing is provided in VISEM through MUULI, the software component for the calculation of matrices.
MUULI allows you to visually aggregate information! You simply highlight the columns or lines and MUULI creates the new district.
Population divided into homogeneous behavioural groups
The population of the area to be analysed is divided into so-called "homogeneous behavioural groups". The groups greatly differ in terms of mobility patterns. However, similar mobility patterns are implied to each single group. The VISEM model separately processes the group data for all calculation steps. The following example divides the population into several groups based on the criteria "Profession/Education/Qualification" and "Mobility":
Homogeneous behavioural groups and the corresponding short cuts (cp. Schmiedel (1984)):
Employed with car | E+c |
Employed without car | E-c |
Not employed with car | Ne+c |
Not employed without car | Ne-c |
Trainees | Tr |
University students | UStud |
Pupils as from grade 5 | P>5 |
Primary school pupils | P<5 |
Children under six | Child<6 |
Trip generation: Activity chains
VISEM is based on the assumption that mobility results from activities outside the house. Here are some examples of activities: They are based on surveys such as KONTIV '89. The activity "Education" is subdivided into further categories.
Job | J |
Shopping | S |
Education: Technical, vocational schools | E |
Education: University, College | E |
Education: Schools starting with grade 5 | E |
Education: Primary school | E |
Leisure time | L |
Home | H |
An activity chain describes the sequence of a person's activities throughout the day such as the activity chain Home - Job - Shopping - Home (HJSH). The activity sequence implies changing locations. Our example generates three routes: HJ, JS, SH.
These activity chains describe a person's average mobility program for VISEM.
