PTV Vissim - Frequently Asked Questions (FAQs)

(#VIS28890)

What are the definitions of the following three vehicle attributes?
1) Following distance (FollowDist)
2) Headway (Hdwy)
3) Safety distance (SafeDist)

1) Following distance (FollowDist): Distance to the interaction object in [m] before the time step if the interaction state is not 'Close up'. If the interaction object is a vehicle, then distance is measured from the front of the vehicle to the front of the preceding vehicle; whereas if it is an object, it is measured from the front of the vehicle to the start of the object. If the vehicle interaction state is 'Close up', then it is the distance to the expected waiting position of the preceding vehicle or to the preceding object.

2) Headway (Hdwy): Distance to the preceding active object in [m] before the time step. If the active object is a vehicle, then distance is measured from the front of the vehicle to the front of the preceding vehicle; whereas if it is an object, it is measured from the front of the vehicle to the start of the object. Note: A vehicle or a red signal head is an active object; a green signal head is an inactive object.

3) Safety distance (SafeDist): Desired safety distance in [m] before the time step. It is based on speed if the interaction object is a vehicle (measured from the front of the vehicle to the front of the preceding vehicle); otherwise it is ax (individual standstill distance).