The format is:
List of 4
$ front: num [1:13, 1:3] 0.559 0.548 0.544 0.577 0.574 ...
..- attr(*, "dimnames")=List of 2
.. ..$ : chr [1:13] "1998" "1999" "2000" "2001" ...
.. ..$ : chr [1:3] "airbagAvail" "airbagDeploy" "restraint"
$ side : num [1:13, 1:3] 0.36 0.366 0.367 0.35 0.348 ...
..- attr(*, "dimnames")=List of 2
.. ..$ : chr [1:13] "1998" "1999" "2000" "2001" ...
.. ..$ : chr [1:3] "airbagAvail" "airbagDeploy" "restraint"
$ rear : num [1:13, 1:3] 0.0507 0.0558 0.0575 0.0498 0.0522 ...
..- attr(*, "dimnames")=List of 2
.. ..$ : chr [1:13] "1998" "1999" "2000" "2001" ...
.. ..$ : chr [1:3] "airbagAvail" "airbagDeploy" "restraint"
$ other: num [1:13, 1:3] 0.0312 0.0304 0.0313 0.0237 0.0254 ...
..- attr(*, "dimnames")=List of 2
.. ..$ : chr [1:13] "1998" "1999" "2000" "2001" ...
.. ..$ : chr [1:3] "airbagAvail" "airbagDeploy" "restraint"