The National Highway Traffic Safety Administration has posted online the results of additional tests performed by GM engineers on recalled Cobalts, HHRs, Ions, and Solstices.
The cars have defective ignition switches that can turn into the "accessory" or off position if a) there is extra weight on the key ring, and b) the switch is jarred, by the car going over rough terrain, for example.
The defect is linked to at least 13 deaths and 31 injuries, although attorneys who have filed lawsuits against GM over the defect claim there are many more deaths and injuries.
The additional tests indicate there has to be quite a lot of extra weight on the key ring to knock the ignition into accessory mode.
In most of the tests, the defect was not triggered until there was .7 pounds of extra weight on the ring.
GM engineers performed the tests at the Milford Proving Ground, where the company maintains simulations of bumpy pavement, potholes, angled railroad crossings and the like.
One lawsuit sought to force GM to tell customers of the recalled cars not to drive them until the ignition switch is replaced. The judge in that case said such an order was properly the responsibility of the National Highway Traffic Safety Administration.
The agency said it relied on GM's tests, which indicate driving the cars with just the key in the ignition is safe.