“Drive safe” should only be used as a parting farewell and has probably come into modern usage because “be safe” is correct. “Drive safely” is correct grammatically when used in all other contexts.
When you want to wish someone get home in their car safe and sound, you can say either “Drive Safe” or Drive Safely.” Both phrases are correct. The only thing you need to pay attention to is context and sentence structure, particularly when writing. Otherwise, you can use either one.
People often say these when someone is leaving after spending some time together, either in person or on the phone. This is common at nighttime when there are potential drunk drivers and wildlife running out on the road. It’s a way to wish someone your protection until they reach their next destination.
The Right Way to Say “Drive Safe” or “Drive Safely”
What’s great is that it is near impossible to use “Drive Safe” or “Drive Safely” incorrectly. That is of course unless you’re writing. Then there are a few instances where you have to pay attention to simple rules of grammar.
Usually, you will say “Drive Safe” or “Drive Safely” at the end of spending time with someone. This can be after you finish talking to someone on the phone and you know they’re going to drive somewhere. Alternatively, you can say it when they’re leaving you to drive to a destination.
Good night Frank and please, drive safely!
Drive safe and thank you for coming to the party.
In the event you’re writing a story, a letter, email, or some other piece, you will have to pay attention to grammar and proper punctuation where appropriate.
You should know how to drive safely by now.
The best way to ensure you drive safely is to check all your mirrors before pulling away.
In these particular examples, “safely” functions as an adverb. It describes the manner in which someone drives. When speaking the phrases, they become more of an expletive. In which case, grammatical rules are more lax in casual speech.
Safe is an adjective that people often use as an adverb. Safely is an adverb so, therefore, should be used to modify the verb “to drive”.
The difference between using “Drive Safe” and “Drive Safely” will come down to if you’re writing or speaking the phrases. Either is correct usage when bidding farewell but you must be careful when writing the phrases in other contexts.