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ACCIDENT MITIGATION and autonomous driving are much in the news these days. Autonomous driving claims to replace the driver in mundane tasks of mobility. By contrast, accident mitigation takes over when an emergency places the driver at risk.
I confess to being less than enthusiastic about the autonomous car. If a person doesn’t want to drive, society already offers an alternative—public transportation. But I’m all for technology coming to our aid when things get over our heads.
Subaru’s EyeSight is a perfect example of this. It monitors traffic ahead and, if necessary, applies the brakes in response to an emergency situation—even quicker than a driver might sense it.
EyeSight has two cameras mounted adjacent to the interior rearview mirror, the pair giving stereographic imaging that’s more accurate than a single radar sensor (as used on some other systems).
The physics of motion dictate that such systems are most effective in city driving, at speeds of 25 mph or less.
On the other hand, if the speed differential, the “closing speed,” is of this magnitude, say 70 mph for the approaching car and 45 for the one ahead, automatic braking can’t prevent the accident, but it can mitigate its severity.
The efficacy of Subaru’s EyeSight system came in evaluations by the Insurance Institute for Highway Safety. IIHS is an insurance-company-funded research organization with a reputation for pushing beyond government safety regulations; e.g., impact testing at 35 mph rather than the fed’s 30 mph; offset crashes as opposed to the traditional frontal-impact testing.
This new IIHS evaluation is part of its 2014 Top Safety Pick+ program. A test vehicle traveling 25 mph approaches a stationary dummy car. The dummy is made of foam, with a metal frame and vinyl cover designed to simulate a car to imaging hardware and software. There’s even provision for a license plate, as many systems use this to differentiate a vehicle from other objects.
In IIHS testing, Subaru’s EyeSight identified the car ahead, gave visual and auditory alarm—and initiated braking automatically.
Among 81 midsize sedans, SUVs and crossovers evaluated, Subaru’s Legacy and Outback were the only ones avoiding a dummy collision. Five others, the Cadillac ATS and SRX, Volvo S60 and XC60 and Mercedes-Benz C Class, slowed enough to earn an IIHS “superior” rating.
An “advanced” rating went to eight other models that achieved impact mitigation, though not to the extent of those rated superior. IIHS gave a “basic” rating to 30 others in the evaluation that had forward collision warning but no automatic braking. The remaining 36 models had neither technology.
The philosophy of automatic brake application is not straightforward. A full hit on the pedal obviously minimizes braking distance; but it’s also the most disruptive in false identification. Gentle braking is error-friendly; but it provides only modest mitigation.
Subaru appears to have nailed it technically. EyeSight is designed for a speed differential of 19 mph or less. (IIHS reported it worked fine at 25 as well.) Upon recognition, its initial braking is at 0.25g, a fairly modest retardation, what one might do approaching a line of cars waiting at a traffic light. Mild alerts of auditory and visual nature accompany this.
If the driver interacts with steering avoidance, the system deactivates. If the driver brakes, the system goes to a second stage, with 0.8g retardation (heavy braking, perhaps invoking ABS). If the driver fails to react at all, EyeSight goes to the second stage automatically with enhanced warnings.
In the U.S., Subaru offers EyeSight as an option on selected Forester, Legacy and Outback models. It’s also offered elsewhere around the world.
© Dennis Simanaitis, SimanaitisSays.com, 2013