if you aren't careful,you will have an accident.前面的那个aren't,

如果你再不小心点,可以要出车祸的.are是be动词,而do是助动词.助动词接的是动词,而be动词接的是形容词或者动词ing形式.
例如:
(1)do
I don't like my brother.He always beats me.
我不喜欢我哥哥,他常打我.
其中的like为动词
(2)be(are/is/am)
I'm pretty and everbody loves me.
我是个漂亮的女孩,大家都喜欢我.
其中的pretty是形容词所以接am
Ps.if you don't look out,you will have an accident.
你说的对