Rear crash protection: GMC

For each seat/head restraint, rear-end crash protection is an assessment of occupant protection against neck injury in rear impacts at low to moderate speeds. Although such injuries usually aren't serious, they occur frequently.

The overall ratings are based on a two-step evaluation. In the first step the geometry (distance behind and below the head of a seated average-size man) is rated good, acceptable, marginal, or poor. Seats with good or acceptable geometry then are subjected to a dynamic test simulating the forces in a stationary vehicle that's rear-ended by another vehicle of the same weight going 20 mph. Seat/head restraints with marginal or poor geometry aren't tested dynamically because they cannot protect taller people in rear-end crashes. These seats are rated poor overall.

In the dynamic tests measurements are recorded on a dummy (BioRID) representing an average-size man. BioRID is designed specifically for rear-end testing at low to moderate speeds. The dynamic ratings are derived from two seat design parameters (acceleration of the dummy's torso and time from impact initiation to head restraint contact with the dummy's head) plus tension and shear forces recorded on the dummy's neck. Overall ratings are based on both geometric measurements and dynamic results.

More about the procedures for rating seat/head restraints

Good Acceptable Marginal Poor

Model	Seat type	Overall rating	Dynamic rating	Seat/head restraint geometry
Acadia 2013	Power leather seat
Acadia 2008-2012 (mfg. after March 2008)	Manual-power cloth seats
Canyon 2004-2012	Bench seats
Canyon 2004-2012	Bucket seats
Envoy 2003-2009	All seats
Safari 2003-2005	Seats with adjustable head restraints		not tested (see note)
Safari 2003-2005	Seats with fixed head restraints		not tested (see note)
Sierra 1500 2007-2013	Manual cloth seats
Sierra 1500 2001-2006	Seats with adjustable head restraints		not tested (see note)
Sierra 1500 2001-2006	Seats with fixed head restraints		not tested (see note)
Sierra 1500 2001-2006	Seats with head restraint tilt lock		not tested (see note)
Terrain 2010-2013	Manual - power cloth seats

Note: Seat/head restraints with marginal or poor geometry aren't tested dynamically because they cannot protect taller people in rear-end crashes. These seats are rated poor overall. Seat/head restraints with good or acceptable geometry are also tested dynamically.

Rear crash protection test details (technical information)

Geometric ratings of other GMC models

Ratings of seat/head restraints in newer model cars are based on restraint geometry and a dynamic test. The Institute has been publishing model-by-model ratings of the the geometry of the head restraints in older models since the mid-1990s. Geometry is the necessary first step toward a seat/head restraint that provides effective protection in rear-end crashes at low to moderate speeds.

More than one rating: Ratings are for individual vehicle models. More than one rating may be shown for a model because vehicle seat options can affect head restraint geometry.

No rating shown/no model year listed: The Institute has not evaluated the head restraints in every vehicle model during every model year. If a rating box is blank or if a model year is not listed, no rating is available. If a box is shaded gray, the model was not manufactured that year.

AHR: active head restraint. These are designed to move closer to the backs of occupants' heads in rear-end crashes. These are not rated for geometry at this time.

Model		2004	2003	2002	2001	1999	1997	1995
Envoy		see table above	see table above
Jimmy/Envoy	2-dr
	4-dr
Safari		see table above	see table above
Savana
Sierra 1500		see table above	see table above	see table above	see table above
Sierra 2500
Sierra 3500
Sonoma
Suburban
Yukon
Yukon XL

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