VISSIM 5.30-05 User Manual

Optional Enhancements of the Model
function. To support the choice model, parking lots have a number of
parameters regarded for selection wich are stored in the [SEL. PARAMETERS] tab,
cf. section 6.4.5.
Relevant Situations
Parking lot choice can take place in the following situations:
► When a vehicle starts a trip at its origin parking lot
► When a vehicle is forced to review its decision by a dynamic routing
decision
► When a vehicle is forced to review its decision by the route guidance
system
In all of these situations, the set of valid alternatives and the parameters of
the utility function may be different. The set of available parking lots for a
choice decision at departure is simply the set of all parking lots that belong to
the destination zone and are open at the time of departure. For parking lot
decisions made because of route guidance or dynamic routing decisions, the
set of valid parking lots depends on the strategy chosen. See the description
of these features in their separate sections.
The utility function of a parking lot is defined as:
U k,
s = αk
, s ⋅ C parking
+ βk,
s ⋅ attraction
+ γ k,
s ⋅ Ddest
+ δk
, s ⋅ Dveh
+ ε k,
s ⋅ fs
where
Cpark = parking cost
Ddest = direct distance between parking lot and the destination zone´s
center of gravity
Dveh = general cost of best route from current vehicle position
fs = availability of free parking spaces
k = index of the vehicle type
s = index of the decision situation (departure, routing decision...)
The availability of free places is computed as the ratio of the free places in
the parking lot in question to the maximum number of free places in all
parking lots in the choice set.
The value “distance from the destination zone” might look strange at the first
glance, since parking lots belong to a zone and zones are not explicitly
defined as network elements. How can they then have a position? The
answer to the first question is that in some situations parking lots in other
zones than the destination zone are considered, e.g. if all parking lots there
are full. Then of course drivers are looking for near other parking lots. The
position of a zone is computed from the positions of all parking lots as the
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