All or nothing assignment method
- It is the simplest route assignment algorithm.
- In this algorithm, flows from every origin to every destination are assigned using the path finding algorithm, and travel time remains unchanged regardless of travel volumes.
- All-or-nothing traffic assignment may be used when delays are unimportant for a network.
- In the first stage, the network description and tree building is made. The next stage is to assign the traffic flows to the minimum path tree.
Limitations
- If time alone is used as the governing factor in selecting the minimum path, the other important factors like cost, distance, safety will be neglected.
- In a network with two or more parallel and close links, the link which is only marginally quicker will be allocated all the trips. The resulting flow pattern may lead to an unrealistic situation.
- Too many vehicles tend to be assigned to more attractive routes. This may cause increasing congestion on these routes, and the technique takes
- All facilities in the network are not effectively utilised.
- If a superior facility is available, say, for example a motorway people tend to prefer to use this facility for longer journeys. This technique does not reflect this tendency
