My first experience with a shared space scheme was in Köniz, Switzerland. I was amazed by how well it worked and how the road users communicated with each other. It was a mystery to me why this design is not used more often, as it obviously had advantages. I tried to find quantitative criteria for the use of such schemes – without much success. That’s when I decided to dedicate my master thesis to shared space concepts and to bring light to the darkness. The main objectives were to set up a microscopic simulation of a so called “free crossing area” (FCA), to compare the results with real data and to assess capacity and traffic quality in generalized shared space-layouts.
The idea: Let the traffic organize itself
“Shared space” aims to improve the quality of streets by placing motorized and non-motorized traffic on the same level. Important elements of shared spaces are a high interaction between traffic modes, self-organized traffic by reducing regulations and the integration of social and traffic behavior in a single street layout. FCA is one possible traffic regime to design a street according to the shared space-idea. By removing all zebra crossings, pedestrians are able to cross the street freely at any point, strengthening the interaction between traffic modes. This street layout has only been used reluctantly until now, one reason being the difficulty to identify the effects of FCA in advance. For this purpose, traffic simulation offers a great opportunity, helping planners assessing different traffic layouts in an early stage.
“Get rid of regulations, pedestrian crossings, road markings and sidewalks and you end up with increased efficiency for all road users – the idea of “shared space” sounds incredible, but it actually works.”
The challenge: How do road users behave when there are no regulations?
Modelling mixed traffic is a challenge, because of the complexity of the interaction between pedestrians and cars in such schemes. In addition to that, conventional traffic simulation software is unable to simulate shared space with built-in functions. That is why I used the COM API of PTV Vissim to be able to implement non-standardized solutions. The interaction between pedestrians and vehicles is modelled based on two types of road users. Users either show “prudential” behavior (give way to other users) or “aggressive” behavior (showing no consideration for other users). The decision, which user will behave in which way, is set by conditional probabilities. In Vissim, this is controlled by event-based scripts. Calibration and validation of the model was performed based on the FCA in Köniz, Switzerland.
The result: FCAs work and can reduce delay
Results show, that, regardless of its simplifications, the simulation model is able to represent vehicle travel times and vehicle continuity very well on a high generalization level. It is accurate enough to allow a comparison of traditional pedestrian crossing designs and FCA with respect to delay and capacity. This analysis shows, that since mean delay for every user in FCA is in most cases lower than in comparison to traditional street layouts as zebra crossings, the regime should always be considered when designing a street, especially in situations of high pedestrian activity.
