自分の歩く速度は、普通の人よりは速いつもりだったが、歩けない老人が使うことがあるシニアカーの速度はもっと速かった。
もちろん車よりは遅いが

I thought my walking speed was faster than the average person, but the speed of the senior car, which is sometimes used by elderly people who can't walk, was even faster.
Of course, it's slower than a car, but...