Crash testing lightweight vehicles

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There is an emerging requirement to downsize personal transport – driven by environmental targets, increasing urbanization and resource scarcity – and to support this transition, the development of an appropriate regulatory framework is required.

Building on earlier EU attempts to standardize rules across member states – most notably 2002/24/EC – the recent Regulation 168/2013 establishes the detailed technical requirements and test procedures for the approval of L-category vehicles, and the systems, components and separate technical units intended for such vehicles. Although a move in the right direction, fundamental differences remain between the regulation of lightweight vehicles and the regulation of passenger cars.

As presently structured, Regulation 168/2013 does not demand crash tests or homologations as applied to passenger cars of the M1 class and defined by the relevant UN-ECE regulations. While there are concerns regarding the crash safety provision of L-category vehicles, due to the relative low volumes of quadricycles in European countries, there are at present no problematic conditions as such.

Based on accident data alone, the question is whether these vehicles require legislating at a European level. However, if the numbers of lightweight vehicles in the fleet were to increase in response to environmental pressures then the higher fatality risk (between 10 to 14 times greater) combined with the greater intensity of use would undoubtedly refocus concerns on their crashworthiness.

One proposal for assessment of the crash safety of the L-category vehicle class (including the L6 and L7 sub-categories) would be to adopt the current testing regime developed for M1 passenger cars. While this is good for leveraging existing knowledge, this approach has limitations.

In this test configuration, frontal force levels (the force at which the front of the car would start to deform) are related to vehicle mass. This is fine for single vehicle impacts. However, in a vehicle-to-vehicle collision, the lighter vehicle would be unable to deform the heavier vehicle at the higher force levels required and would likely absorb more than its share of the impact energy leading to compromising of the compartment as a consequence. The present situation is that although there is significant variation in the vehicle mass for the European vehicle fleet it mainly relates to the extremes.

Indeed, studies have shown that 80% of vehicle-to-vehicle accidents have a mass ratio (between the collision partners) of 1.6 or less. Replacing a significant part of the vehicle fleet with lightweight vehicles with a mass of 750kg or less would see a mass ratio in vehicle-to-vehicle accidents significantly higher than this.

As an example, the mass ratio for a 750kg vehicle in a collision with the average European vehicle mass of 1500kg would be 2. There is also a cost element to consider in extending the existing M1 test to the L-category. A report by the UK Transport Research Laboratory quoted the cost of aligning the quadricycle (L7 and possibly L6) requirements with M1 vehicles to be in the region of €700,000 (US$772,965).

Nevertheless, to date several quadricycle manufacturers, including the market leaders Aixam-Mega and Ligier-Microcar, have voluntarily built their vehicles to comply with existing M1 crash standards in order to avoid losing sales through adverse publicity around this issue. Such initiatives by the market leaders may, however, not be feasible for some of their smaller competitors.

To improve the safety of lightweight vehicles would require an innovative regulatory framework that provides benefits to consumers, producers and society. Taking the lead in imposing new regulatory frameworks may also give rise to competitive advantages if later on the respective frameworks diffuse to other markets. In this case, companies operating in the early regulating country may gain early mover advantages in the respective technology.

July 26, 2016

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