Interchanges are an important element in the road network of the Netherlands. This is where an exchange of traffic between highways and secondary roads is possible. However, not all interchanges are functioning optimally. The main problems that occur around interchanges concern the traffic flow and safety. This research wants to explore the possibility that alternative forms of interchanges solve these problems. The research questions are as follows: 1. What affects the lay-out of an interchange ?; 2. How can the quality of an alternative design be evaluated ?; 3. How can the alternative designs contribute to solving the problems at interchanges ? This study provides insight into what issues affect the design of an interchange and integrates these issues together with possible interchange designs into an assessment framework. In order to do this, the pros and cons of different interchange designs are considered. The assessment framework can then help in making design choices for new or modified connections. There are several aspects of the design of an interchange that have to be taken into account. The function of the interchange in the network is important, as is the right-of-way required by the proposed interchange. During the design of traffic constructions it is always important to pay atten-tion to the safety of road users and the principles of Sustainable Safety. In order to be able to find the right interchange design one must also have information about the required capacities. What amount of traffic will use the interchange and at what times? Special issues here are slow and freight traffic. More towards the detailed design, there are various statutory requirements and design guidelines which also must be met. Finally, there are costs, which in itself may not be too high, but must also be reasonable, compared to the benefits. In the assessment framework the most im-portant aspects are considered. The literature review delivers remarkable results. There are sources available that show various unconventional interchange types capable of competing both in terms of flow and in terms of road safety with the more common interchange types in the Netherlands. Especially the diverging diamond interchange and the contra-flow left interchange are attributed a high performance. The single point urban intersection has fewer advantages in terms of applicability and is more dependent on certain conditions, such as the absence of slow traffic. Literature review shows that the most interesting interchange types for inclusion in the assessment framework are the compressed diamond intersection, the bone roundabout, the contra-flow left interchange, the single point urban intersection and the diverging diamond interchange. These alternatives are preferred above the double on- and off ramp, the multiple-lane roundabout and the turbo-roundabout with traffic lights. Those alternatives have either too much influence on the traffic on the highway, are unsafe or are too expensive. The five alternatives are simulated with the program VISSIM. In this program they are subject to eight intensity distributions. The following variables were used: intensity on secondary road, intensity on on and off ramps, the presence of slow traffic and the amount of freight traffic. The performance is evaluated based on five different indicators: the total travel time, total delay, average delay, average waiting time and the amount of non-arrived vehicles. Based on the results of this simulation the contra-flow left interchange and, at lower intensities, the diverging diamond interchange turn out to be alternatives with a good traffic flow. By combining the results of the literature study and the computer simulation an assessment framework can be established. To make the use of this framework as simple as possible, it is de-signed as a tree. This way, only the most necessary considerations need to be made during the design process. This study shows that there are oppor-tunities to compensate problems with the flow and safety at interchanges with alternative forms of interchanges. This study brings an assessment framework that guides in choosing the right al-ternative, in a way that provides the user clarity about what the beneficial points of a certain design are. (Author/publisher)
Abstract