reduce speed

decelerate impede

bar block dam halt hinder moderate obstruct slacken slow stop

slow down

advance aid allow assist continue encourage forward free help let go liberate open permit promote push unblock

accelerate

abate curb curtail decelerate decrease diminish hinder impede lag lessen moderate reduce relax retard slacken stall temper

brake check choke detain loiter mire postpone procrastinate qualify quiet reef regulate stunt

anchor it back-water bog down cut back cut down ease off ease up embog hit the brakes hold back hold up keep waiting let down flaps lose speed lose steam rein in set back wind down

advance agitate aid allow assist develop encourage enlarge excite expand extend facilitate forward further grow help increase lengthen prolong push raise strengthen

accelerate do expedite liberate release