# Collisions and overlaps in path-guided navigation

In AnyLogic 8.5.2 the movement algorithm of the transporters with path-guided navigation has been improved for a more realistic performance during possible collisions at the intersections and on neighbouring paths. Below you can find the major points of improvement illustrated.

The size of the rectangles in the images matches the dimensions of the AGVs. The arrows indicate the direction of movement.

 An AGV that has stopped or is moving slowly An overtaking AGV A possible overlap between the two AGVs according to the previously realized logic of the path-guided AGVs movement

## Overlaps

#### Previously

The AGVs could overlap while moving through different intersections (including the point nodes minimized to single points) as displayed in the images below.

#### Now

The overtaking AGV can see the AGV in front of it and stop at the distance specified in Min distance to obstacle parameter. This is realized for AGVs moving both on the same path and on different paths. The overtaking AGV also slows down as soon as it sees the AGV in front of it.

## Collisions at intersection

#### Previously

The AGVs meeting at a point node could overlap, but still would move through the intersection without a collision.

#### Now

If the intersection is implemented with a point node resized to minimum or the diameter of the node is less than the value specified in Min distance to obstacle parameter, then a collision occurs. In the image below the red AGV cannot avoid bumping into the green AGV while moving through the intersection.

## Collisions on neighbouring paths

#### Previously

If the paths in the network were too close to each other, the AGVs would overlap and proceed without a collision.

#### Now

The AGVs would stop to resolve a collision.

## Resolving collisions

#### Previously

The collisions could only be resolved inside the nodes, therefore some AGVs would wait for the incoming AGV at the node for a long time. When the AGVs met at the node, a collision would occur and then the AGVs would move along overlapping each other.

#### Now

A collision can be resolved on the path. In the situation described in the image above, the red AGV doesn't have to wait for the green AGV at the node. They will meet on the path and move along after a timeout specified for collision resolving. Visually, the AGVs will stop on the path during the specified timeout and then move along overlapping each other.