As part of the Integrated Transport Plan to support the Kaiapoi Town Centre Plan, ViaStrada has developed intersection options and concept designs for Williams Street, the main thoroughfare through the town centre. One option includes a redesign of the existing roundabouts to better cater for pedestrian crossings and truck turning movements. One of the intersections featured a particularly acute angle presenting a design challenge and potential stakeholder acceptability issues. Many trucks have to undertake the acute right turn to access a cool store or supermarket and as such some truck drivers avoid this right turn, prefering instead to approach the intersection from the west and travel straight through the roundabout. The concept design for this intersection involves offsetting one of the intersection legs to create two seperate intersections.
The concept designs were developed in AutoCAD using AutoTrack software to check heavy vehicle tracking curves.
Design tolerances were low and to confirm the assumptions made in the design process, project team members and stakeholders participated in a tracking test at the former Wigram Air Force Base. The proposed design was set out on the airfield using chalk and sawdust filled bags.
A semi-truck and trailer unit and coach were then driven through the simulated roundabout.
The results of the test confirmed that our tracking software is accurate. However, the software settings used were shown to be conservative, as the professional drivers exhibited greater manoeuvrability. For some movements it was shown that the design could be tweaked to narrow approaches and enhance pedestrian mobility. The test also helped improve stakeholder support for the proposed design.
Clients can have confidence that ViaStrada's designs will be feasible and will minimise implementation risks.
Two further video clips, of a semi-trailer with a steering axle and of a tour coach, are available on YouTube.