VISSIM 5.30-05 User Manual

6 The Traffic Network
► if vehicles leave from the network immediately after passing the
overlapping section (since there is no connecting turn starting from that
section)
A conflict area can be used to model the following conflict types:
► Crossing conflicts (one link crosses the other)
► Merging conflicts (two connectors lead to the same link or one connector
leads to a link that has other traffic coming from upstream)
► Branching conflicts (two connectors come from the same link or one
connector comes from a link that continues further downstream)
The driving behavior of vehicles approaching a conflict area provides the
maximum possible flow-rate for the minor road without interfering with the
traffic on the main road. (In case of merging areas vehicles entering from the
minor road may interfere with the traffic on the main road, depending on the
user-defined safety distance factor: The smaller the factor the stronger the
interference.)
► A vehicle on the minor road approaching a conflict area (where it must
yield) determines if there will be a sufficient gap in the major road
movement when it arrives at the conflict area (with its current travel plan,
i.e. if it ignored the conflict area). If there is no such a gap, the vehicle
decelerates as if it had to stop in front of the conflict area. In the next
time step the vehicle calculates again, so it can possibly cancel the
braking and continue even with a certain acceleration, "aiming" at a later
gap.
► A vehicle on the main road tries not to "crash" into vehicles on the minor
road. If it determines that a vehicle on the minor road will still be inside
the conflict area when it arrives there, it brakes to stop in front of the
conflict area. (As this deceleration causes it to arrive later, it can possibly
continue its journey without further braking in a later time step so that it
passes just behind the vehicle on the minor road.)
A vehicle on a minor road will try not to enter a crossing conflict area if there
is not sufficient space downstream of the conflict area to leave the conflict
area immediately. This means that a vehicle enters the first conflict area of
several adjacent conflict areas (without room for the whole length of the
vehicle in between) only if it can pass all these conflict areas in one
continuous movement.
With a conflict area of the crossing type, also a vehicle of the major flow
intends to keep the conflict area clear as long as this vehicle belongs to the
percentage that has been specified via the Avoid Blocking property, cf.
section 6.6.2.3
Conflict areas of the merging or branching type are not kept clear of
major flow vehicles. To keep conflict areas of the merging or branching
type clear, a priority rule has to be defined, cf. section 6.6.1.5, example 2.
Vehicles on the minor road do not enter if they must assume that they cannot
leave the conflict area before the next vehicle on the main road will arrive
(plus safety gap, cf. section 6.6.2.3).
272 VISSIM 5.30-05 © PTV AG 2011