Yes. You can legally overtake the vehicle, but only if it is safe and you stay within the speed limit.

Quick Scoop: What This Question Is Really Asking

This classic test question is checking whether you understand that:

  • You may overtake a slower vehicle on a road where the speed limit is higher.
  • You must not exceed the posted speed limit to complete the overtake.
  • You must only overtake when it is safe and using the correct lane (normally to the right on Australian roads).

So the intended “correct” answer is:

Yes, once it is safe to do so.

Breaking Down the Options

Typical multiple-choice options for this question are:

  1. No
  2. No, because it's a 100 km/h road.
  3. Yes, once it is safe to do so.
  4. Yes, as long as I overtake to the left.

Why option 3 is correct:

  • The vehicle is doing 85 km/h in a 100 km/h zone, so it is below the limit. There is no rule that says you cannot overtake just because it is a 100 km/h road.
  • Road rules allow overtaking as long as you:
    • Do not go over the speed limit.
    • Only overtake when you have enough clear road and visibility.
    • Follow lane markings and signs.

Why the others are wrong:

  • “No” / “No, because it’s a 100 km/h road.” – Incorrect because overtaking is allowed below the speed limit when safe; the 100 km/h limit is a maximum, not a minimum.
  • “Yes, as long as I overtake to the left.” – In Australia you normally overtake to the right ; left-side overtaking is only allowed in specific situations (e.g., the other vehicle is turning right or in certain marked lanes).

Key Safety and Legal Points

When overtaking in this situation, you must:

  • Stay at or below the signed speed limit (e.g., 100 km/h).
  • Check mirrors and blind spots, and ensure you have enough clear road ahead.
  • Obey any solid lines, “No Overtaking” signs, or other restrictions.
  • Return to your lane only when you are safely past the other vehicle.

A simple way to remember it:

If it’s below the limit, clear ahead, legal to pass, and you can stay under the limit – you may overtake, but you never must.

Mini FAQ

Do I need to overtake just because they’re slow?
No. If you are not comfortable or conditions aren’t right, stay behind at a safe following distance. Can I speed briefly to overtake?
No. You are not allowed to exceed the speed limit specifically to complete an overtake, even if it might feel safer in the moment.

TL;DR: The vehicle ahead is travelling at 85 km/h in a 100 km/h zone; you can legally overtake it once it is safe to do so and without speeding.