which of the following sentences is even more correct?

  • There is a slow moving vehicle ahead.


  • there is a slowly moving vehicle ahead.

What is the difference between them.

To me, the second one sounds more correct as “slowly” modify moving, on the other hand the first one sound awkward as “slow” is modifying the the gerund “moving”. It means adjective cannot modify gerund, moving.

  • It is usually better to put the modifying adverb after the verb. I would prefer "There is a vehicle ahead moving slowly." if you want to emphasize the speed of the vehicle. "slow moving vehicle" emphasizes the kind of vehicle.
    – user3169
    Mar 13, 2018 at 1:52

3 Answers 3


They are both correct and mean almost the same thing, but with a very slight difference.

There is a slow-moving vehicle ahead.

By using the compound adjective "slow-moving," you are implying that moving slowly is an intrinsic property of the vehicle. It's moving slowly right now because it is the type of vehicle that usually moves slowly (e.g., a garbage truck).

There is a slowly moving vehicle ahead.

By using the adverb "slowly," you are really only describing the movement right now and nothing about its habitual behavior. Maybe it's an ordinary car that just happens to be moving slowly at the moment because the driver is texting on his phone or something.

Which one is correct will depend on the situation and the type of vehicle you are talking about.

  • +1. How about There's a veehickle ahead movin kinda slow? Could it be either?
    – TimR
    Mar 13, 2018 at 21:29

In the first sentence, slow is adjective which says something about the vehicle, i.e. it is a slow vehicle. Suppose we changed the sentence a bit, then it would be clearer:

There is a large reversing vehicle ahead.

Then it's clear that large says something about the vehicle, whereas reversing says something about the vehicle.

In the second sentence, slowly is an adverb which says something about moving, i.e. it is moving slowly.

You probably want to say that there is a vehicle ahead which is moving slowly, so you should choose the last sentence:

there is a slowly moving vehicle ahead.

  • Good answer, but maybe address which one is more correct since that was part of the question?
    – Element115
    Mar 13, 2018 at 3:31

The correct answer is

There is a slow moving vehicle ahead.

it meaning the vehicle is moving slowly down the street, whereas

There is a slowly moving vehicle ahead.

can mean that the actions of the vehicle are slow, for example a street cleaning machine, and its slow movement may be interpreted to be causing the vehicle to move down the street slowly.

For example

The spider slowly moved across the table

The spider's movements were slow, it's legs moved slowly, and implicitly the spider crossed the table slowly also.

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