According to the CRAN page, the current version of the package pbkrtest (v0.4.6) requires R v. 3.2.3 or higher.
Depends: R (≥ 3.2.3)
Since car depends on pbkrtest, you need to upgrade your R version to the latest version in order to use this package.
Alternatively, you can install an older version of pbkrtest (0.4.4 or higher), which you can find here. Version 0.4.5 of pbkrtest could be a good choice if you don't want to or cannot upgrade R, because this version would be sufficient to install the latest version of car, and it could operate on your current R version since it requires only R v3.0.2 or higher.
