The three premium mid-sized sedans were found to offer low levels of protection for drivers in the Institute’s new ‘small overlap frontal crash test’, which sees 25 per cent of a vehicle’s front end strike a rigid barrier at 40mph (64.4km/h) on the driver’s side.
The test is designed to replicate what happens when the front corner of a car collides with another vehicle or a fixed object like a tree or a pole – the kind of crash that accounts for around one-quarter of frontal crashes involving serious injuries or fatalities to front-seat occupants.
The IIHS says outside of a small number of car manufacturers’ proving grounds the test is not currently conducted anywhere else in Europe or the US.
The Volvo S60 and the Acura TL were the best performing vehicles in the test, both earning ‘good’ ratings.
IIHS president Adrian Lund says the majority of today’s new cars are designed to ace moderate frontal offset crash tests, in which 40 per cent of the front the car impacts a rigid barrier, like those conducted by NCAP and the National Highway Traffic Safety Administration (NHTSA) in the US. The main crush-zone structures in vehicles are concentrated in the middle 50 per cent of the front end, leaving the outer edges under-protected and increasing the propensity for crash forces to go directly into the front wheel, suspension and firewall.
The Volvo S60 performed the best from a structural point of view. With only a few inches of intrusion, the IIHS said the occupant compartment looked much the same as it did after the moderate overlap test. The IIHS says reinforcement of the S60’s upper rails and a steel cross member below the instrument panel help to keep the safety cage intact.
In contrast, the Lexus IS had approximately 10 times the level of occupant compartment intrusion as the Volvo. The A-pillar bent at right angles and the footwell collapsed as the left front left wheel and tyre were forced rearward, trapping both of the dummy’s feet.
The right foot of the dummy in the Mercedes-Benz C-Class was also trapped during its test as the front wheel was forced in towards the footwell.
The Volkswagen CC scored slightly higher than the Lexus and the Mercedes with a ‘marginal’ rating, but claimed the unfortunate honour of becoming the first vehicle to completely lose its door in an IIHS crash test.
Restraint systems also have a vital role to play in protecting occupants in small overlap frontal crashes. In the Lincoln MKZ, the steering wheel was pushed so far towards the centre of the cabin that the dummy’s head missed it completely, while the curtain airbag failed to deploy fully, leaving the driver’s head almost entirely unprotected.
One or both of the side and curtain airbags failed to deploy in seven of the 11 vehicles evaluated, and of the six curtain airbags that deployed, four didn’t provide sufficient forward coverage.
Lund said designing vehicles that performed well in 25 per cent frontal crash tests was the next crucial step in improving occupant protection.
"Nearly every new car performs well in other frontal crash tests conducted by the Institute and the federal government, but we still see more than 10,000 deaths in frontal crashes each year. Small overlap crashes are a major source of these fatalities," he said.
The IIHS says the latest small overlap frontal crash test results will not affect the ‘Top Safety Pick’ status of a number of the vehicles tested, but has flagged changes to its criteria from 2014 to penalise vehicles for sub-standard performances in the test.