# Passing the DVSA theory test

I recently passed by DVSA theory test, which is a requirement for sitting the practical driving test to legally drive on UK roads. I booked my theory test 3 days ago, grabbing a last minute slot for earlier today, having not studied before then. Normally the waiting time is around 3 weeks, but when checking for future availability I spotted a late cancellation and grabbed it, then made plans to frantically study.

The tests are split into a 50 question theory test, with multiple choice answers, and a “hazard perception” test where you are shown a driving scene where you must click on potential hazards as they arise. There are plenty of guides available for studying for the tests, but the only ones I would trust are the official DVSA ones. You don’t want to fail part of the test by following an incorrect, unofficial guide that might be out of date (for example, in 2013 the DVSA updated the hazard perception test from live video to CGI, making a lot of practice videos obsolete). They’re not that expensive, either.

### Software

I was about to download the DVSA theory test PC software, but later found that they provide a mobile phone app that does the same thing. I normally try to avoid apps, because the screen is small and I don’t like giving them access to my phone, but in this case the difference in price was significant (£5 vs £15 for the same software). I also didn’t want to risk the software not working on Linux via Wine, which is what I use (badly written Windows software often can’t be properly emulated on Linux).

#### Theory

Almost all of the theory questions can be studied for simply by reading the Highway Code once, carefully, and using common sense; and of course doing lots of practice questions to check your understanding. You can even skip the parts of the highway code specifically for cyclists, motorcycles and trucks/heavy goods vehicles if you’re lazy, as these won’t be tested directly. Ensure you cover the road signs, as there are many and they aren’t all ones you’d have observed regularly on roads where you live.

The Highway Code took me about 3 hours to read, and I did this first before using the app. The app contains hundreds (~750) of questions, some of which will be asked in the actual test, and written guides to the Highway Code sections. Reading everything in the app, and doing the practice tests for each section, took me about 10 hours split over two days. Mock exams of 50 questions took about 15 minutes each, and I did four or five of those. My average score was 49/50.

##### Thinking, braking and stopping distances

Questions in the test can involve thinking distances, i.e. the distance travelled by the car between a hazard occurring and you processing it and braking, braking distances, i.e. the distance travelled by a car between you applying pressure to the brake pedal and the car coming to a halt, or both of those combined – the stopping distance. For these distances, you are supposed to just learn the numbers for speeds of 20 to 70 miles per hour. The Highway Code lists the following:

Speed (mph) Actual thinking distance (m) Actual stopping distance (m)
20 6 12
30 9 23
40 12 36
50 15 53
60 18 73
70 21 96

While I could have memorised these numbers with a bit of effort, I find it easier to remember formulae so I came up with some equations. For the thinking distance, simply multiply the speed by 0.3:

$$\text{thinking distance (m)} = 0.3 \times \text{speed (mph)}$$

This gives you the exact thinking distances. For total stopping distances, including thinking and braking, multiply the speed by 1.5, then divide by 100, then add 0.3, and multiply what you get by the speed again:

$$\text{total distance (m)} \approx \text{speed (mph)} \times \left(0.3 + \frac{1.5}{100} \times \text{speed (mph)} \right)$$

This equation is not exact, but the largest error it generates is 1.5 m, which allows you to easily select the correct answer from the multiple choice answers.

Speed (mph) Actual stopping distance (m) Calculated stopping distance (m) Error (%)
20 12  12  0
30 23  22.5  2.17
40 36  36  0
50 53  52.5  0.94
60 73  72  1.4
70 96  94.5  1.6

It may be possible that you are asked about just the thinking distances or braking distances. For the braking distance, calculate first the total stopping distance and subtract the thinking distance ($$0.3 \times \text{speed (mph)}$$), or leave out the $$0.3$$ term in the total stopping distance equation.

#### Hazard perception

To get the hang of hazard perception, you not only need to train your eye to learn what potential hazards look like, but also learn how to play the game the software presents: if you want to score points, you can’t click on a hazard too late, nor too early. Each hazard has an unseen window in which you score from 5 to 0 points, with quicker response in principle giving you higher scores; however, some hazards have weirdly late scoring windows and I was often caught out when practising having clicked too early on something I knew to be a hazard, meaning I got 0 points. Ridiculous! I therefore changed my strategy to click multiple times on each hazard, in case the window had not yet started by the time of my first click. This is a risky strategy, because the software monitors your clicks and fails you if you are perceived to be gaming the system by clicking on everything that moves or in a pattern. I failed a few of the practice tests by clicking too much, which is frustrating because I was not trying to game the system but just click within the scoring window.

It turned out the app only contained 10 example hazard perception scenarios, which was woefully little. To give myself extra training on hazard perception, I paid for access to the DVSA’s online hazard perception course. It reports that it provides 100 examples, but some of these (around 40) are not actual hazard perception tests, but multiple choice questions. You are shown a similar scene to a hazard perception test, but some time in the video the scene freezes and you are asked something about what you should have observed (such as “Which lane should you be in” when an approaching motorway lane merges from the left). These are still useful, as it trains you to observe signs, but it’s not exactly what you will be tested on in the real thing.