Sentence:  He can ( 1 ) point his car resolutely at the invading fender and force the other driver back into Lane A ; ( 2 ) slow down and permit the ambivalent driver to change lanes ; or ( 3 ) alternately accelerate and <WSD>decelerate</WSD> , thus keeping the first driver guessing as to his intentions , thereby making a fascinating sport of the whole affair . 
Meaning of the word marked with <WSD> tags:  lose velocity; move more slowly