Modeling overtaking maneuvers on the lane of oncoming traffic

You can model overtaking maneuvers during which the overtaking vehicles use the lane of oncoming traffic. This for instance allows you to simulate the overtaking of PuT vehicles temporarily stopping in an urban area, on a link with a single lane only, or the overtaking of slower vehicles outside of the city. You can model multiple vehicles overtaking and multiple vehicles being overtaken. The overtaking vehicle shall only then perform the overtaking maneuver, if there is no oncoming traffic which excludes the option of overtaking.

In Vissim a vehicle wants to overtake when it's desired speed is considerably higher than that of vehicle preceding it (0 m/s to 4 m/s, normally distributed, around mean value 2 m/s). The vehicle then checks the following requirements in order to be able to perform the overtaking maneuver:

• At overtaking speed, it would take the vehicle at most 4 seconds to drive into its preceding vehicle. The overtake speed is the desired speed plus the attribute overtaking speed factor (OvtSpeedFact).
• Its link has a passing lane (Attributes of links).
• The passing lane must overlap with the inner lane of the oncoming lane. The width of the overlapping area is not relevant. The z value of the oncoming lane and of the passing lane must not deviate more than 0.5 m from each other.
• The overtaking area, which consists of links and connectors that overlap with the oncoming lane, must be at least long enough for a vehicle to be able to perform an overtaking maneuver.
• Downstream of the last vehicle that is to be overtaken, there must be a large enough gap visible, so that the passing vehicle is able to change back into its previous lane after completing the overtaking maneuver. The largest gap must be at least one passing vehicle length, plus double the safety distance from the front and rear of the vehicle, as required during standard car following behavior.
• The overtaking maneuver must be able to be completed safely, without endangering oncoming traffic. The vehicle recognizes oncoming traffic on the opposite lane from a certain distance. This distance is defined for the link of the opposite lane in its attribute Look ahead distance for overtaking (LookAheadDistOvt). The vehicle that wants to overtake safely assumes that anywhere beyond this distance there will be oncoming traffic. To assess the course of the trip of oncoming traffic, Vissim uses the attribute Assumed speed of oncoming traffic (AssumSpeedOncom) of the oncoming lane (Attributes of links). Vissim does not account for any additional vehicles following the oncoming vehicle.

The figure below shows the following in 2D mode:

• a section of a link 1 that runs from left to right via a lane 11 and a passing lane 12 (hatched) with right-hand traffic running from left to right. Vissim displays passing lanes with hatched lines as soon as its link has at least two lanes and the attribute Has passing lane is selected.
• a section of a link 2 that has only one lane in right-hand traffic, running from right to left. Link 2 was created as an oncoming lane of link 1 and fully overlaps with passing lane 12.
• For overtaking maneuvers on link 1, vehicles driving from the left to the right use passing lane 12.
• Vehicles on link 2, driving from the right to the left, cannot be overtaken, as link 2 does not have a passing lane.
• The gray vehicle that is overtaking on passing lane 12 recognizes that there is no vehicle in the opposite lane within the distance defined in the attribute Look ahead distance for overtaking (LookAheadDistOvt) of link 2.

The overtaking vehicle reduces its speed to the desired speed, as soon as it leaves the passing lane.

An overtaking vehicle may cancel its overtaking maneuver, if downstream of the vehicle it is overtaking, the gap in its previous lane is not yet large enough to change back into it. This may be the case when there is suddenly unexpected oncoming traffic or the vehicle that is being overtaken accelerates. When a vehicle cancels an overtaking maneuver and wants to change back into its lane, the vehicles behind it can reduce their speed to allow for the lane change.

The driving behavior of oncoming traffic is not influenced through the overtaking maneuver.

When the length of the overtaking areas is checked, this is done along the current route or path of the vehicle. This way, vehicles without a current vehicle route or path cannot overtake on the oncoming lane.

The vehicle width is not considered a criterion for the option of an overtaking maneuver. It is generally assumed that there is not enough space on the oncoming lane for oncoming traffic and a passing vehicle to drive next to each other .

Before an overtaking maneuver takes place, Vissim does not account for network objects on the oncoming lane, e.g. reduced speed areas, signal controllers or stop signs. However, as soon as the overtaking maneuver starts, the passing vehicle reacts to these network objects.

When a vehicle changes from a link with a passing lane to a connector without a passing lane, the connector then has one lane less than the link with a passing lane. In this case, the distance defined in the attribute Lane change distance (LnChgDist) also specifies the minimum distance to the connector at which an overtaking maneuver may be started. Passing on the oncoming lane is not possible within this lane change distance.

If the conditions for automatic speed limitation in curves are met, the vehicle reacts and can reduce its speed during the overtaking process (Changing the desired speed).

Passing on oncoming lane for both movement directions

You can model overtaking maneuvers for both movement directions. In this case, an additional passing lane is placed on top of the inner oncoming lane. This means the passing vehicles of both movement directions use the oncoming lane and need to account for any oncoming traffic.

The figure below shows the following in 2D mode:

• a section of a link 1 that runs from left to right via a lane 11 and a passing lane 12 (hatched).
• a section of a link 2 that runs from right to left via a lane 21 and a passing lane 22 (hatched).
• Links 1 and 2 are placed so that their passing lanes 12 and 22 each overlap with the lane of oncoming traffic, so that vehicles can pass in both movement directions.