VISSIM 5.30-05 User Manual

6 The Traffic Network
VISSIM supports multiple conflict markers (green bars) for each stop line
(red bar). Thus multiple rules can be applied to the same stop line.
Both the stop line and the conflict marker(s) can be defined for certain
vehicle classes only. In addition, a maximum speed can be defined for
vehicles on the major road: Then only vehicles that approach the conflict
marker at a speed below the max. speed will be considered by the headway
of the priority rule.
Conflict markers and stop lines can be defined by lane or by link. Thus
modeling can be simplified. However, for lane-specific parameters or
different stop line positions, lane-specific stop lines and the appropriate
number of markers need to be defined.
Depending on the scenario to be modeled either the gap time or the headway
can be of higher importance. Vehicles waiting for the chance to enter or
cross a flow of higher priority usually regard the gap time. On the other hand,
the headway is used to find out, if a vehicle of higher priority has already
reached a certain position.
Additionally the relevance depends
on the flow on the link where the
conflict marker is located.
In case of normal traffic flows, the
gap time is the relevant parameter,
whereas the headway is decisive in
case of bumper-to-bumper traffic and
congestions.
For a selected priority rule, min.
headway > 0 is displayed by a green
triangle indicating the direction of
traffic at the given position on the
link.
The conflict marker recognizes vehicles on all connectors that enter the
link before the position where the conflict marker is located. This behavior
causes problems if the waiting vehicle is also recognized by the conflict
marker, for example, if the waiting vehicle is within the headway range of
the conflict marker. To avoid this problem, a conflict marker on a link
should always be placed at a position upstream of the position where any
relevant connectors enter that link.
If vehicles appear to be ignoring priority rules this could be the reason:
If at a set of priority rules one or more vehicles wait for themselves or one
another (gridlock situation) then VISSIM recognizes the gridlock and
resolves it: Then the vehicle with the longest waiting time comes first.
260 VISSIM 5.30-05 © PTV AG 2011