The MoT Files: The Story Behind The Data

The HonestJohn.co.uk MoT Files is the most detailed analysis of MoT data ever to be carried out. We’ve crunched the numbers and scoured more than 355m records, 200m MoTs (all those since the system was computerised in 2006) and 40gb of data. Take our word for it, this was no easy task.

In fact, until 2010, VOSA - the body responsible for MoTs in the UK – openly refused to supply the material, but the information commissioner ruled that disclosure was in the public interest and overturned VOSA's refusal. Thankfully, things have improved since 2010 and VOSA now issues regular MoT data updates. All of the information you see here is sourced from the Government’s OpenData website - which houses all the data that's released into the public domain.

Crunching the numbers isn’t without its problems and we’ve had more than a few (dozen) issues with the data provided by the Government. Firstly, it's huge and difficult to work with. Secondly, as it's sourced from thousands of technicians, it is littered with mistakes and errors.

Indeed, during our analysis we’ve found plenty of cars registered in the 1800s and a few steam-powered Renault Clios to boot. Then there was the structure; one person's BMW 320 is another's BMW 3 Series - if we went with the VOSA data as it was, we would have ended up with a huge amount of separate BMW 3 Series models (and 1, 5, 6 and 7 Series for that matter) - amongst others. Plus there were the complications of generations, bodystyles and other variants.

We've done our best to ensure the MoT data you see here is as clean as possible, by classifying it by make, model and year of registration. In our opinion, this is the first time anyone has provided a complete breakdown of MoT performance.

To make the information more accessible, we have broken down a lot of the data into top and bottom 10s. In our opinion this gives a superb insight into how the best and worst makes and models perform at the MoT. In most cases, we’ve limited the MoT tests to 5000+ to get a better impression of how mainstream manufacturers perform. However, you can get a direct breakdown for all makes and models from the MoT Files’ home page, here.

What we are publishing goes into more detail than ever, showing makes and models going back to 1980, information about tests in 118 postcode areas and how mileage affects the MoT test.

But don't take our word for it, jump into the MoT Files for yourself to see how all makes and models perform