EDIT 7/8/18: Our NCT work featured in the Sunday Independent: https://www.independent.ie/life/motoring/car-reviews/which-car-is-best-of-the-test-37185356.html 

In Ireland, every car over 4 years old requires a roadworthiness certificate, which it gets bypassing the National Car Test (NCT). If you’re buying a used car, it’s important to know how likely that make and model is to pass the NCT – and if it fails, on what part of the test.

To help you find out this information, Idiro has analysed the results of the last 5 years’ NCT tests – and we offer you two tools:

The NCT checker

Idiro has created a simple NCT car checker tool, available online. You’ll find it at www.Idiro.com/NCTchecker.

Just enter the make, model and year of the car in question to learn all about how these cars perform in the NCT. If your car is quite rare, like the Mazda MX-5, then we recommend that you select all the years of NCT tests. Otherwise, just leave 2017 ticked.

As you can see, Mazda MX-5s from the year 2000 have a 66.3% failure rate across 5 years of tests – just slightly worse than the average of 65.7% for all cars of that age. However, look at the detail – the MX-5 does much better than average for some elements (no failures for suspension!) but much worse for others (four times worse for emissions). That will help you know what to look for when buying a used car, and help you prepare your car to maximise its chance of passing the NCT.

Idiro's NCT checker - input form and results

Our handy NCT checker works on phones, tablets and PCs. Kudos to my colleague John Grant for building it.

Exploring all of this year’s NCT results

For people who would like to dig deeper into the NCT results, we have produced an interactive dashboard as a demonstration of our data analytics skills.


Again, it uses data published by the Road Safety Authority covering 2017 NCT tests. Data has not been published on retests, so our dashboard covers the first NCT test that each car underwent in 2017.

For practical purposes, the data is filtered to show only the twenty most popular makes of vehicle tested in 2017, and for each of these, only models with at least 1000 tests in the year. This was necessary because to show every make and model of the car tested would make the dashboard so complex as to be unusable. As a result, from the total 1.4 million tests carried out in 2016, 1.1 million tests are represented in this dashboard.

However, if you do want to look at the makes and models of cars that are not shown in this analysis, you can download the full dataset from the RSA.

How to use this dashboard

Pro tip: To reset all your filters and return to the original screen, click your browser’s refresh button.

The RSA provides the ‘Year of Car’ of each car tested, which we understand to mean the year of first registration. You can filter by the age of cars using this slider. For example, if you want to see test results for all cars registered in 2010 or before, you simply drag the end buttons in the slider over to the desired year.

This is an interactive dashboard, so as you change one parameter, all of the graphs adjust to match your selection. For example, this bubble table shows the top 20 most popular makes of car with a 2010 or older registration. The bubble’s size indicates how popular that make is, and its colour indicates the make’s pass rate – from deep blue (high pass rate) to deep red (low pass rate).

Test volume and pass rate per make

In this example, we can see below that for vehicles registered in 2010 and older, Toyota is the most popular make and has a high pass rate.

Now let’s click on ‘Toyota’. As you can see, this changes all the charts in the dashboard – they now only show the details of Toyota models.

Toyota selected

Pro tip: To compare different car makes, hold down the CTRL key while you click on each make that you want to filter in the bubble chart “Overall Popularity & Passing % of Model”.

Now let’s examine the different Toyota models. In the next graphic to the right, ‘First-time pass rate by model’, you’ll see the pass rate of each Toyota model.

First time pass rate for Toyotas

In the table on the far right entitled ‘Most Popular Model & Age’, you’ll see each model in the Toyota range. The Prius is the Toyota with the highest pass rate, but it isn’t the most popular Toyota – as you can see, the Corolla is the most popular (as you will see, Corollas have been around since 1980).

As you scroll down, you can see the ‘First Time Failure By Year’ graph which shows the number of cars tested (blue bars) and failure rates (red line) for each year of registration. As you can see, younger cars are much more likely to pass the NCT. To look at failure rates over time in each category within the test, you can filter by category in the drop-down menu.

First Time failure

To the right, you’ll see the ‘First Time Failure By Category’ table, which shows the percentage of cars that fail each category within the NCT test. This image displays what caused Toyota cars to fail their NCT.

As you can see, the dashboard allows you to dig deep into the 2017 NCT test results. Here again, is the link to the dashboard:


This dashboard works best on PCs, rather than mobiles. Kudos to colleagues Paul Goldsberry and John Grant for building it.

We do hope you find these tools useful. To discuss how Idiro’s analytics skills can help your business, drop us an email at info@idiro.com.  To download the source data from RSA.ie, click here.



Recommended Posts