Since the man is performing an action, I believe the correct translation would be 남자가 자동차 앞에서 걸어요 (~에서 instead of ~에).
Use ~에 when no action is being performed, like 남자가 방에 있다. (The man is in the room.) Use ~에서 when there is an action, like 남자가 방에서 읽는다. (The man reads in the room.)
And if I am not mistaken, ~로/으로 also mean "using". Example: 제가 안경을 바나나로 청소 해요. "I clean my eyeglasses with a banana." So tessabanessa is quite correct in calling it a "method particle". With respect to locations/directions, I always translated it as "towards" or "in the direction of" ... but Duo didn't accept "towards" as correct (today). : (
I would like to add the discussion. Basically, I agree with the translation.
Particle -에 and -으로 are totally different.
남자가 자동차 앞으로 걸어요 The man is located far or there is a significant distance between the man and the car. So, he walks towards the car.
남자가 자동차 앞에 걸어요 The man is near the car and walking in front of the car.