Is it obligatory to exchange greetings every time drivers enter and exit the restaurant, knowing that their number may reach 200 times during working hours?

Spreading greetings of peace (salam) is a confirmed Sunnah and a manifest ritual, and returning the greeting is obligatory. If two Muslims meet, one greets the other with salam. If they separate and then meet again—even if only a short distance apart—it is Sunnah for one to greet the other with salam. This greeting should be repeated every time they meet, and returning the salam is obligatory. This repetition is recommended but not obligatory, and whoever returns the greeting once has fulfilled the essential Sunnah.