Failed G tests in Ontario tend to have a lot in common. While there’s a lot that happens on the road that’s outside of your control, DriveTest examiners are required to grade students on a standardized marking scheme. As a result, the reasons for failing the G road test are fairly consistent. While everybody knows that running a red light or driving well above the speed limit will cause you to fail, the most common reasons for failing are a lot more subtle.

Here are the top 5 most common reasons for failing the G test:

1. Merging onto the highway too slowly

Highway driving is one of the core skills being tested when you’re going to get your G. To pass your G test, you need to demonstrate that you can merge onto a highway safely, drive at the correct speed, change lanes, execute an emergency stop, and then safely exit the highway. Where a lot of individuals trip up is on the one area that seems the simplest – entering the highway safely. While everybody knows that driving well above the speed limit can lead to you failing, driving below the speed limit can be equally dangerous. If the speed on the highway is 100 km/h, for example, you should be merging onto the highway as close to 100 km/h as possible. Merging too slowly can lead to failing your road test, since it increases the risk of a collision with a faster-moving vehicle behind you.

2. Improper emergency stop execution

As part of your G test, you’ll be asked to perform an emergency stop – either on a residential street or on the highway. To properly execute an emergency stop, you’ll have to signal to the right, safely exit the highway, turn on your hazard lights, put on your hand brake, and then put the car in park. Forgetting any of these steps will make your examiner think that you don’t know how to properly perform an emergency roadside stop. To increase your chances of success, practice roadside stops both on and off the highway, going through each of the steps methodically. The steps for performing a roadside stop are the same whether you’re driving on the highway or a quiet residential street – as a result, you may want to practice roadside stops in a quieter area until the process feels automatic.

3. Improper following distance

Following distance is defined as the space between your vehicle and the car in front of you. To practice safe driving – and avoid failing your G test – it’s critical to leave sufficient room between you and the car in front of you. Confusingly, though, following distance is typically measured in terms of seconds rather than distance. In good weather – and at low speeds – you’ll want to leave at least two seconds of space between your vehicle and the car in front of you, according to the MTO’s driver handbook. The worse the weather – and the greater your speed – the more space you’ll need to leave. “Tailgating”, or maintaining too close of a following distance, can increase your risk of a collision, and consequently lead to failing your G test. If you’re following the car in front of you too closely, you’ll have insufficient time to react in case they brake suddenly. As a result, make sure to maintain a following distance of at least 2 seconds – but often more – on the day of your road test.

4. Inconsistently checking your mirrors

By checking your mirrors consistently, you’ll be showing your examiner that you’re aware of your surroundings. To pass your G test, you’ll need to check all three mirrors – left, right, and top / centre – every 5 to 7 seconds. Your examiner likely can’t see your eyes moving, though, so to show them that you’re checking your mirrors, you’ll need to move your head rather than just your eyes. Failing to check your mirrors – or failure to adequately demonstrate to your examiner that you’re checking them – can lead to failing your G test. To be on the safe side, remember to check your mirrors every 5-7 seconds and move your head slightly to make this clear to your examiner.

5. Improper lane merging

To pass your G test, you’ll be required to demonstrate that you know how to safely merge and change lanes – both on and off the highway. To properly merge, you’ll need to look for a gap in traffic, check your mirrors and blindspot, signal, merge at the same speed as traffic is moving, and then turn your signal off. Failure to perform these steps in the correct order will result in a failure. Merging is a common source of collisions on the road, so your examiner will be particularly sensitive to whether you’re performing the steps correctly.


While many reasons for failing the G test are common knowledge, others are much less obvious but equally severe. Failing the G test is avoidable, though, with proper practice. Keep these 5 tips in mind on the day of your road test, and good luck!

If you’re looking for a bit of practice before going for your G test and need to book driving lessons, click here.