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approval approach where safer vehicles are prioritised in access decision-making. The development of a modular PBS approach was first suggested in 2012 during the review of the PBS scheme. The NHVR now has advanced vehicle performance modelling capacities and more engineers with expertise within PBS, which provides a framework and opportunities to dive deeper into the modular concept. “Under a modular concept we would create a modular approval system. For example, the prime mover’s powertrain may be assessed against the PBS standards without the specific knowledge of the trailers connected to it. The high-speed dynamics and lowspeed performance of a combination is mainly influenced by the trailer characteristics. It would be possible to approve a certain prime mover to operate with trailers that are within a performance and design envelope,” Les says. “So instead of specifying every unit in a PBS combination, we would specify these performance design envelopes, which would represent a framework of this modular approach. That would be beneficial as operators would able to assemble PBS compliant applications.” At present the NHVR has a PBS Vehicle
Approval for an operator with 11 trucks and ten trailers. According to Les that vehicle approval is 141 pages long after all the individual units and combinations are drawn up and specified individually. “Managing the assessment and certification of a large fleet is very difficult and challenging from both an operational and compliance perspective ,” he says. “It would be great if operators could say ‘I’ve got this PBS Level 1 modular trailer and I’m looking for a new prime mover — what is on your list?’ The manufacturer could then go over their PBS Level 1 modular options and purchase that prime mover and operate it without having the new PBS assessment done. That’s the logic behind it.” Given there are many technical assumptions involved, getting there will be complex and not without significant challenges, once the vagaries of vehicle performance and the pathway to describing these facets are factored into the process. Removing some of the PBS vehicle combinations from the scheme and then transitioning them back to the prescriptive fleet was one of the original principle objectives of PBS when Les first started working on it in 1999. He cites the proforma designs for new
non-standard vehicle designs that meet the performance-based Standards in New Zealand. The approved non-standard vehicle combination designs have been introduced to streamline the approval process for applying for high productivity commercial vehicles. “It would be great to create these type of classes of proforma designs,” Les says. “For some of the higher mass and longer combinations, New Zealand’s approach has used PBS to create proforma designs and transport operators can use combinations that meet those specifications. There are currently 14 proforma designs available and these designs specify the length, axle spacings, widths and other dimensions based on PBS. Transport operators can approach the manufacturer and say ‘build a vehicle to this specification.’ When you get that vehicle you don’t need to do a new PBS assessment.” Between the truck and dog combinations and A-doubles that are being accepted in the jurisdictions, according to Les, there isn’t a great difference between them in terms of their length, axle-spacing, the componentry and suspensions. “It would be possible to create these envelopes if only we had the legislative framework supporting this concept,” he says.
Three-axle Mack tipper and four-axle dog the most popular PBS combination under the scheme.
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