9.1 Traffic Assignment Flashcards
The final step in the transportation forecasting process.
traffic assignment
____ is used to predict the actual routes and traffic volumes on highways and streets.
traffic assignment
This method takes the origin-destination (O-D) pairs from earlier forecasting steps and assigns each trip to a specific route, whether by car or transit.
traffic assignment
By summing up the routes across all segments, planners can estimate the _____ for each route.
average daily or peak-hour traffic volume
This forecast helps determine the capacity and potential congestion levels on urban transportation networks.
traffic assignment
This method is similar in approach to a mode choice curve.
diversion curves
The traffic between two routes is determined as a function of relative travel time or cost.
diversion curves
The _____ method assigns all trips to those links that comprise the shortest time path between the two zones.
minimum time path
The ____ is based on the theory that a motorist or transit user will select the quickest route between any O-D pair.
minimum path assignment
The results can be depicted as a tree, referred to as a _____.
skim tree
Advantages
1. simple
2. inexpensive
3. results are easy to understand
Disadvantages
1. assumes all traffic will pass through one path
2. creates unrealistic flow patterns
all-or-nothing assignment
The number of trips assigned to each link is compared with the capacity of the link to determine the extent to which link travel times have been increased by the additional volume placed on the formerly empty link.
capacity restraint
Using relationships between ____ and _____ (speed), it is possible to recalculate the new link travel time.
volume, travel time
_____ assign a portion of the trip exchanges (i.e. in chunks) between zone pairs while updating the travel times between increments.
incremental method
_____ = function of volume that is assigned thus far
new travel time
