Literal equestrian tool worn on a rider's heel to urge a horse forward.
The cowboy spurred his horse and galloped away.
spurring on; impetus; acceleration
Figurative use: something that stimulates or accelerates a process, often in the pattern ～に拍車をかける.
The introduction of new technology spurred changes in the industry.
His remark added to her anxiety.
The jockey spurred the horse's flank to make it run.
The rapidly accelerating urban development is causing problems.
促進 refers to deliberate, steady promotion of something, whereas 拍車 evokes a sudden, dramatic acceleration like spurring a horse.
拍車 (spur) and 拍手 (clapping/applause) share the kanji 拍 and similar sound, but refer to completely unrelated things.
Compound of 拍 (beat, clap) and 車 (wheel, vehicle). Originally referred to a spur used in horse riding, later extended figuratively to anything that provides impetus.