There are less car accident this year than there were last y

正确的说法是：
There are less car accidents this year than there were last year.
也就是说,accident（单数）错了,应该是复数accidents,比去年少也不会少到只有一起交通事故,再者说,句首的there are 也确定了后面名词要用复数,主谓在数量上一致,都是复数.