The design of category N3 vehicles for improved driver direct vision

Previous research has shown that existing Category N3 vehicle designs exhibit considerable direct vision blind spots in front of and to the near (passenger) side of the vehicle. This research explores the potential to reduce these blind spots through changes to vehicle geometry made possible by the proposed increase to vehicle length. Using a concept vehicle designed in a project performed by FKA this research evaluates the direct vision afforded to the driver against a baseline DAF XF 105 and a range of iterations of the FKA concept to explore improvements to vision. The analyses are performed using a 3D projection technique in the SAMMIE digital human modelling system. This allows the vehicle concepts to be populated with representative drivers and visual targets including vulnerable road users in the form of pedestrians and cyclists and a typical Category M1 vehicle (a passenger car). The analysis has shown that these blind spots can be improved for the specific tests that have been performed in this research by the FKA concept and the iterations of the concept that have been produced by the LDS team. When compared to the baseline vehicle the original FKA concept improves direct vision to vulnerable road users located at the centre of the vehicle front as the extended front effectively pushes the visual targets further away from the front of the vehicle allowing them to be seen. The visibility to the two front corners of the FKA concept and the lateral visibility through the driver and passenger doors remain problematic. The first iteration of the FKA concept reduces obscuration through the design of a compact instrument panel similar to those used in bus and coach designs. This iteration also improves direct vision to the near side and front nearside corner of the vehicle through the use of additional glazed areas. The visibility of the offside front corner is still problematic. The second iteration of the FKA concept is a modified version of the first iteration with a reduction in the cab height of the vehicle by 230mm. This results in the most successful concept analysed, with good direct vision of all of the visual targets that have been defined in the research project. This reduction in height is possible with current vehicles but would result in a vehicle with reduced off road capabilities due to a reduction in ground clearance. The third iteration of the FKA concept explored the potential of a central driving position. This provides advantages to direct vision through improved lateral visibility at the original height of the concept vehicle. However, this iteration also introduces new direct vision issues. The project has shown that the potential to extend the front of category N3 vehicles to include aerodynamic features has some benefit in terms of improved direct vision for the design that has been analysed, but that more radical design solutions, such as lowering the vehicle cab, and adding glazed areas to the doors and below the windscreen bottom edge provide more effective solutions to the direct vision problem.