The traffic volume induced by planning projects (e.g. in the context of environmental impact statements) is usually calculated exclusively on the basis of the new traffic created by the project (gross traffic induction). Secondary effects like transfer of traffic from other destinations or changing traffic patterns induced by the project are neglected. This may result significant errors in assessing the impact of a project on the environment. Therefore, a method to calculate the net traffic induction is developed.
This research aims to develop a straightforward and uniform strategy for the assessment of planning projects generating large traffic loads and to establish corresponding guideline values.
- Module 1: preliminary stage.
- Module 2: Evaluation of existing data.
- Module 3: Further surveys and interviews.
- Module 4: Summary of results of modules 2 and 3 (empirical section).
- Module 5: accounting for the effects of using a traffic model.
- Module 6: Synthesis, development of "clean method".
- Module 7: Summarize the conclusions and recommendations for practice.
- Module 8: Final Report.
In order to calculate the Net-Driving Performance correction factors were established
which are applied to the Gross-Driving Performance: These were defined by taking into
account the following alternatives to direct access:
- Chaining: A combination of different trips with (generally) different purposes. The chaining correction distributes the total driving performance to the different purposes estimates the part of driving performance to be ascribed to the VE in question.
- Hopping: When several VE are situated in one single location (e.g. a ’Shopping Mile’) the total driving performance of the location in question is distributed to the single VE’s at this location.
- Substituting: When a new VE is established some of the customers may have visited a different VE before. Their Net Driving Performance of these customers is the difference of the driving performance of the new and the old VE.
The correction factors are based on personal interviews with 2’500 visitors at seven VE’s
(Zentrum Bläuacker in Köniz, Wankdorf Center in Bern, Wynecenter in Buchs/AG and
four VE’s situated in the ’Shopping-Mile’ Lyssach/Alchenflüh) representing different types
of situation (integrated in settled area, peripheral, isolated) and several types of VE
(Shopping Center, ‘Fachmarkt’ i.e. large hardware stores, home improvement centers
and similar retail chains). The numbers of interviews allow stable and well-founded conclusions with regard to Chaining and Hopping.
Correction factors are between 0.5 - 0.8 for Chaining and 0.5 - 0.7 for Hopping respectively.
This means that Gross-Driving Performances can overestimate the net-values
by up to 50%. Furthermore, since these two corrections are independent, the correction
factors can be multiplied. In extreme cases this could lead to very marked reductions of
the Gross-Driving Performance.
In the case of substitution corrections of 50% to 100% were observed. The small number
of example observed however precludes generalizations of these numbers.
It is recommended to use the following correction factors. For Chaining and Hopping
between 0,5 - 0,9 for substitution between 0 - 1. The specific value to be chosen depends on the individual case.