Hello, I’m Martin from PTV Group.
Precision is one of the greatest advantages of PTV Visum when it comes to demand modeling. As the focus in transport planning moves away from new road construction towards traffic management, greater accuracy is required.
This is where Activity Based Modeling, or ABM, comes into play.
First, let me explain the traditional modeling methodology.
In a classical demand model, the mode choice is based on the average travel time between the centers of traffic analysis zones. As you see here, the shortest path from one zone to the other starts with a connector, then uses a PT service, and then again, a connector. At first glance, this seems to be an acceptable simplification. But let's take a closer look and zoom in.
The decision for or against public transport depends crucially on the walking distance to the stop. The zone center is representative for all residents, but its distance to the bus stop is comparable to only a subset of residents, here marked in red. Zones are often not homogeneous, especially those that are more on the periphery of the planning area.
The classical demand model wouldn’t probably choose any PT trip from this zone, since the distance to the bus stop is too far from home, it is about 700m. And this may be true for those who live near the zone center. But for those who live near the bus stop, they might take the bus.
A classical demand model lumps all residents of a zone together and uses average values. The Visum ABM is an HD model, that means spatially fully disaggregated. It calculates walking and travelling times individually for each location. Take, e.g., the path between the blue locations. The walk paths are quite short compared to the zone average; it is quite likely that one takes the bus in this situation.
The Visum ABM is also temporally disaggregated, it calculates the travel and waiting times for each time-of-day period. While a classical 24-h model knows only one time period, as this screen should illustrate, Visum’s ABM differentiates between time periods: in the morning during AM peak, the roads are heavily occupied, a person may take the bicycle for her trip.
In the night, the roads are nearly empty, and one could take the car.
Due to its high resolution, the Visum ABM offers a much more precise choice model than classical demand models do. Instead of averages, exact travel times are used, corresponding to the correct time periods.
This is important whenever PT supply quality or road saturation fluctuates during the day. In addition, small trips are far better modeled, what includes access trips to PT stops as well as active modes like bicycle, scooter and walk.
PTV Visum 2022 is now available for download. As we continue to develop new Visum features, we’d love to get your feedback. So let’s chat at the PTV Visum Forum on LinkedIn.