Blind Spots — What They Are and How to Check Them

Blind spots are one of the simplest road-safety ideas to understand — and one of the easiest to get badly wrong in practice. Most learner drivers know mirrors matter. Fewer fully appreciate that mirrors do not show everything. A cyclist, motorcyclist, or car can still be hidden in an area just outside your mirror view, even when you are using your mirrors correctly. This guide explains what blind spots are, how to set your mirrors properly, when to do a shoulder check, and what the RSA expects from you in the driving test.

What a Blind Spot Is

A blind spot is an area around your vehicle that your mirrors do not fully cover. Even with three correctly adjusted mirrors — interior, left and right — there are gaps in what you can see. A road user can be present in one of these gaps without appearing clearly in any mirror.

The RSA Rules of the Road directly refers to checking blind spots, if appropriate, for traffic following behind when you are preparing to change position. That wording is important because it acknowledges a simple truth: safe driving is not just about using your mirrors. It is about knowing where your mirrors stop helping and what to do about it.

Every vehicle has blind spots. Their size and location vary with the height, width, and mirror configuration of the vehicle, but they exist on all cars, vans, trucks, and buses. Understanding yours — and respecting those on other vehicles — is a core part of safe driving.

How to Set Your Mirrors Correctly

Before you can understand what mirrors miss, you need to know how to set them so they show as much as possible. The RSA Rules of the Road gives specific guidance on mirror adjustment, and it is covered in the very first session of Essential Driver Training (EDT).

Interior (rear-view) mirror

Adjust the interior mirror so you can see the full rear window with as little of the vehicle's bodywork showing as possible. You should be able to do this without moving your head significantly — just a slight tilt is enough. The goal is to see the road directly behind you, not the parcel shelf or the headrests of rear passengers.

Left door mirror

The left door mirror should show a small strip of the vehicle's left side at the inner edge, with the majority of the mirror showing the road and lane to the left and rear. You need to see the lane beside you and the edge of the kerb when it is relevant.

Right door mirror

Set the right door mirror the same way — a thin strip of the vehicle's right side visible at the inner edge, with the road and lane to the right filling most of the mirror. When both door mirrors are set correctly, you should be able to see approaching vehicles transition from one mirror to the other as they pass.

What correctly set mirrors still cannot show

Even with all three mirrors set perfectly, there are areas beside and slightly behind your vehicle that remain hidden. The typical blind-spot area on a standard car is roughly level with your rear door or rear quarter-panel, to the left and right of the vehicle. A cyclist or motorcyclist in that position will not appear clearly in any mirror, no matter how well adjusted they are.

Why Mirrors Are Not Enough

Mirrors give you a wide picture of what is happening around your vehicle. But they cannot give you a complete picture. The door mirrors have angles they simply cannot reach — particularly the area beside and just behind the rear of the car. A motorcycle travelling at speed, a cyclist filtering through slower traffic, or a car that has pulled up alongside you may be in exactly that area without being visible in any of your mirrors.

This is not a failure to use mirrors correctly. It is a structural limitation of mirror systems that no amount of adjustment eliminates entirely. It is why RSA guidance for both learners and testers builds in the idea of a final shoulder check — called a safety glance — before any change of direction or position is made.

Think of it this way: mirrors tell you what is generally happening behind and beside you. A safety glance confirms that no one is hiding in the one area the mirrors cannot reach, just before you commit to moving.

What a Safety Glance Means

The RSA defines a safety glance as the final check over either the left or right shoulder to cover the blind-spot area that cannot be seen in the mirrors, made immediately before a change of direction. The key word is final. The safety glance is not the first thing you do — it is the last thing you do before you move.

In practice, this means:

• You check your mirrors first (interior, then relevant door mirror)
• You signal if appropriate
• You make your final safety glance over the relevant shoulder
• If the area is clear, you proceed with the manoeuvre

The glance itself should be quick and deliberate. You are looking for a specific thing — a road user in the blind-spot area — not gazing vaguely sideways. RSA tester guidance is clear that the glance must be over the shoulder, not simply a look into the mirror again. Looking into an already-checked mirror a second time does not cover the blind spot.

Blind Spots and the MSM Routine

The Mirror-Signal-Manoeuvre (MSM) routine — also referred to as MSMM (Mirror-Signal-Mirror-Manoeuvre) in RSA EDT guidance — is the structured sequence every learner driver in Ireland is taught for approaching hazards, junctions, and any change of direction or speed.

Blind-spot checks sit inside this routine. The full sequence looks like this:

The safety glance is not a separate idea bolted onto the MSM routine. It is embedded in the final mirror check before you commit to the manoeuvre. Understanding this is important for learner drivers because the examiner is watching for the whole sequence — not just individual elements in isolation.

When to Check Your Blind Spot

Blind-spot checks are needed any time you are about to move into a space that might contain another road user who is not visible in your mirrors. RSA standard driving-test procedures identify the following as situations requiring a look around:

The RSA Rules of the Road specifies checking blind spots "if appropriate" — meaning your judgment matters. You are not expected to throw your head over your shoulder at every slight steering input. The check is for situations where another road user could genuinely be hidden in the blind-spot area. In practice, that means most lane changes, moves from the kerb, and turns at junctions on roads with any meaningful traffic.

Cyclists, Motorcyclists and Hidden Road Users

Blind spots are especially dangerous for vulnerable road users. Cyclists and motorcyclists are narrower than cars, travel at different speeds, and can occupy spaces that drivers do not instinctively expect. A cyclist filtering slowly along the left side of traffic, or a motorcyclist overtaking at speed, can both pass through the blind-spot area in the time it takes to check a mirror and begin moving.

RSA cycling guidance specifically notes that all vehicles have blind spots and that cyclists should be particularly careful around large vehicles. But the duty on drivers is equally clear: if you are turning left, changing lane or pulling away from the kerb, do not assume a cyclist is absent simply because the mirror looked clear a moment ago. Traffic — particularly two-wheeled traffic — moves faster than people expect.

Pedestrians stepping out

Pedestrians — particularly those crossing from the left when you are turning — can also be in a position that your mirrors did not capture. A shoulder check before a left turn catches both the cyclist alongside and the pedestrian already in the crossing. It is not just about cyclists; it is about anything smaller than a car that may have moved into the space since your last mirror check.

Large-Vehicle Blind Spots

The blind spots on large commercial vehicles — trucks, buses, HGVs — are significantly larger than those on ordinary cars. RSA heavy-vehicle guidance highlights that many large vehicles have blind areas extending directly in front of the cab, along both sides, and behind the trailer. The RSA specifically mentions Class VI "cyclops" mirrors, which are fitted to reduce the blind area immediately in front of heavy vehicles — a problem that simply does not exist on cars.

RSA cycling guidance gives a useful and direct rule: if you cannot see the driver's face in their mirror, the driver cannot see you. This applies whether you are a cyclist, a pedestrian, or another driver positioned alongside a large vehicle. If you are not visible to the driver, you are in their blind spot.

Four key blind zones on a large vehicle

For ordinary car drivers, the lesson from large-vehicle blind spots is twofold. First, understand and check the blind spots on your own vehicle. Second, respect the much larger blind spots on trucks and buses by staying out of them — particularly when a large vehicle is turning or manoeuvring.

Common Blind-Spot Mistakes

Blind Spots in the Irish Driving Test

The RSA driving test examiner will observe your mirror use and shoulder checks throughout the test. Blind-spot checks are not assessed as a single isolated item — they are part of the broader assessment of observation, lane discipline, and road position. However, certain moments are consistently watched for a shoulder glance:

• Moving off — a right-shoulder glance before pulling away from the kerb
• Turning left at a junction — a left-shoulder glance to check for cyclists immediately before the turn
• Turning right — a right-shoulder check before committing to the turn
• Lane changes — a shoulder glance in the direction of the change
• Merging — checking the relevant blind spot before joining moving traffic

A single missed check at a quiet moment may be recorded as a minor fault. A missed check at a critical moment — where a road user was actually present or could reasonably have been — is more serious. The examiner uses professional judgment, but consistent absence of shoulder checks across the test will be noted.

Key Points for Learners

• A blind spot is a physical area around your vehicle that mirrors cannot fully show — it is not a mistake, it is a limitation of the mirror system.
• Set all three mirrors correctly before moving off: this reduces your blind spots as much as possible, but does not eliminate them.
• The RSA Rules of the Road says to check blind spots, if appropriate, when changing position or direction.
• A safety glance is the final over-the-shoulder check before changing direction — it is the last step before the manoeuvre, not the first.
• Blind-spot checks sit inside the MSM/MSMM routine: mirror, signal, mirror (safety glance), manoeuvre.
• Cyclists and motorcyclists are the road users most often in blind spots — especially when you are turning left.
• Large vehicles have significantly larger blind spots than ordinary cars. If you cannot see the driver, the driver cannot see you.
• On the driving test, make your shoulder checks clear and deliberate — the examiner needs to see them.

Frequently Asked Questions