In January, I released an analysis of how often doors were jammed in the NHTSA full frontal crash test from 1979 to 2008, and found out that doors were becoming jammed less often over time. During the same period, crash test results improved, so it would stand to reason that vehicles that had jammed doors would, on average, have worse injury measures than those with operable doors. But does correlation imply causation here?
I found some surprises during my analysis. The 1984 Pontiac Fiero was among the best performers, with HICs in the 300s and Chest G's near 30 for each occupant, but both doors were jammed. The 1980 Honda Prelude's doors were both operable, but the HICs were fatal: 3,063 for the driver and 1,778 for the passenger!
I decided to compare vehicles with jammed doors to vehicles with operable doors from the same time period to see which had lower average injury measures. The driver door was used for the comparison; vehicles with an operable driver door (whether easily or with difficulty) were placed in the "operable" group, and those with a jammed driver door (that required tools to open) were in the "jammed" group. The 1979-1993 model years were compared; these were the years where it was relatively common to see both operable and jammed doors. After 1993, jammed doors became rare, comprising less than 20% of the test vehicles.
1979-81, operable - Driver: 1,275 HIC, 56 Chest G's. Passenger: 1,170 HIC, 45 Chest G's. 27 vehs.
1979-81, jammed - Driver: 1,372 HIC, 55 Chest G's. Passenger: 1,452 HIC, 49 Chest G's. 28 vehs.
1982-84, operable - Driver: 932 HIC, 45 Chest G's. Passenger: 784 HIC, 40 Chest G's. 29 vehs.
1982-84, jammed - Driver: 979 HIC, 50 Chest G's. Passenger: 1,076 HIC, 42 Chest G's. 40 vehs.
1985-87, operable - Driver: 1,070 HIC, 49 Chest G's. Passenger: 869 HIC, 43 Chest G's. 46 vehs.
1985-87, jammed - Driver: 1,147 HIC, 52 Chest G's. Passenger: 1,006 HIC, 41 Chest G's. 48 vehs.
1988-90, operable - Driver: 922 HIC, 50 Chest G's. Passenger: 758 HIC, 45 Chest G's. 67 vehs.
1988-90, jammed - Driver: 1,145 HIC, 54 Chest G's. Passenger: 963 HIC, 45 Chest G's. 34 vehs.
1991-93, operable - Driver: 754 HIC, 50 Chest G's. Passenger: 691 HIC, 46 Chest G's. 80 vehs.
1991-93, jammed - Driver: 923 HIC, 55 Chest G's. Passenger: 967 HIC, 49 Chest G's. 25 vehs.
Although both sets of vehicles showed improvement with time, for every model year grouping and occupant, the injury risk averaged higher on vehicles with jammed doors than vehicles with operable doors, and generally the difference was quite significant.
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