In recent years the semi-rural Thomas/Gordonton intersection has become increasingly busy, used by around 16,000 vehicles per day. Between January 2017 and January 2018 there were 19 crashes.
In October 2018 the speed limit on the approach to the intersection was reduced from 80km/h to 60km/h as recommended by the Business Case, however more needed to be done to slow drivers down. Hamilton City Council wanted an upgrade to the intersection to improve traffic flows and support its Vision Zero aspiration to achieve zero road deaths and serious injuries within Hamilton.
The original intersection had a give way t-intersection on a horizontal curve with 8% super elevation that had a number of concerns that needed addressing. These included identification as a high-risk intersection, not catering for alternative modes of transport, congestion leading to driver frustration and risk taking, and high speeds (760 vehicles per day exceeding the posted speed limit of 80km/h).
While the obvious solution to slowing traffic was to install a roundabout, site restrictions and the urgency for safety improvement meant it wasn’t a viable short to medium term solution for the intersection. We recommended the installation of traffic signals and together with Hamilton City Council and the National Safer Intersections Working Group, agreed to trial raised safety platforms (RSPs) as part of a safe system solution. This was to slow high-speed traffic down to 50kph as it approached the traffic lights.
This concept was a first for NZ and required interpretation of overseas studies and guidelines to ensure fit for purpose at this particularly site. Our research specialist’s in road/vehicle dynamics undertook detailed analysis of our specific design to ensure minimal risk of truck/bus rollover. To minimise safety risks to our staff, the site survey was undertaken at night using 3D laser scanner technology, which allowed survey staff to remain off the live roadway.
By working closely with Hamilton City Council, Waka Kotahi – the NZ Transport Agency and the contractor, we successfully delivered the upgrade of the existing priority-controlled intersection to traffic signals with RSPs. Post-construction monitoring shows that speeds have already reduced to predicted values and locals are reporting safer driving behaviour.