2680 reviews
Driving Theory 4 All

Not quite, but now you know for next time!

Your tractor unit has 3 air lines. You're connecting to a trailer that has 2 air-line couplings. What colour is the line you should not connect to the trailer?

Red
You selected this answer
Blue
Correct answer

DVSA explanation

When connecting a three-line tractor unit to a two-line trailer, the blue line is the one that should not be connected to the trailer. This is the auxiliary line. Always follow the manufacturer's advice: it may be necessary to reconnect the extra line to the tractor unit.

Want more free practice?

Take a free HGV / LGV practice theory test

Ready to test yourself on the latest DVSA revision questions?

Get full HGV / LGV theory test practice

Continue your free practice

More free ways to get ready for your DVSA HGV / LGV theory test.

Take a free HGV / LGV mock theory test Take a free HGV / LGV hazard perception test Take a free road signs practice test
Not what you were looking for?
Find out what we offer for every DVSA theory test by selecting the theory test you want to prepare for.
Car
Theory Test
Motorcycle
Theory Test
ADI Part 1
Theory Test
LGV
Theory Test (part 1a and 1b)
LGV CPC
Module 2 Theory Test
PCV
Theory Test (part 1a and 1b)
PCV CPC
Module 2 Theory Test

Industry leading reviews from 2680 verified buyers...

Read More Reviews
Driving Theory 4 All Reviews
Driving Theory 4 All on X

Keep up to date with us on social media...

Your motorcycle theory test covers more than just road signs. 🏍️ Prepare with motorcycle DVSA revision questions, hazard perception clips and unlimited mock theory tests. Get 365 days' access from £5.99 👇 https://t.co/8lt9yJFTl5 #motorcycletheorytest
14 hours ago
Revising for HGV theory test Parts 1a and 1b? 🚛 Prepare for the multiple-choice and hazard perception tests with DVSA-licensed revision material, mock tests and progress tracking. Explore our LGV theory test packages 👇 https://t.co/69qYzDyQF3 #hgvtheorytest
1 day ago
Theory test question 🚨 What type of emergency vehicle uses a green flashing beacon? Would you recognise it on the road? Check your answer and read the explanation 👇 https://t.co/hGxShF6n9g #theorytest
1 day ago
Spotting a hazard is one thing. Knowing when to react is another! 👀🚗 Improve your timing with FREE hazard perception test practice and get feedback on your performance. Practise spotting developing hazards before your DVSA theory test 👇 https://www.drivingtheory4all.co.uk/free-hazard-perception-test #hazardperception #theorytestpractice
2 days ago
Planning to book your UK theory test? 🚗📅 Book your car or motorcycle DVSA theory test with Driving Theory 4 All and get access to revision materials to help you prepare. Choose your preferred DVSA test centre and date 👇 https://www.drivingtheory4all.co.uk/book-theory-test #booktheorytest #theorytestbooking
2 days ago
Ready to test your driving theory knowledge? 🚗📝 Try our FREE mock theory test with 50 questions, just like the multiple-choice section of the real DVSA car theory test. Get instant marking and see if you can reach the 43/50 pass mark 👇 https://www.drivingtheory4all.co.uk/car-mock-theory-test #mocktheorytest #theorytest
2 days ago
Prefer learning by watching? 🚗📚 Our car theory test practice includes animated tutorial videos, DVSA revision questions and unlimited mock theory tests. Choose how you revise, with packages from £5.99 👇 https://t.co/HP7zW9uBMT #cartheorytest #theorytest
2 days ago
Need to arrange your theory test booking? 📅🚗 Book your car or motorcycle theory test with Driving Theory 4 All and get revision materials included to help you prepare for test day. Find out how to book your theory test 👇 https://www.drivingtheory4all.co.uk/book-theory-test #theorytestbooking #booktheorytest
2 days ago
Preparing for your driving theory test? 🚗📚 Get ready for your theory test with our AI Personal Trainer, the latest DVSA practice questions, hazard perception clips, mock theory tests and Highway Code revision. Start your theory test practice today 👇 https://www.drivingtheory4all.co.uk/ #theorytest #drivingtheorytest
2 days ago
PCV Driver CPC Module 2 coming up? 🚌 Practise with 60+ case studies and topic-based revision material designed to help you prepare for the real test. PCV CPC practice costs £14.99 👇 https://t.co/oBmxWgrg10 #drivercpc #PCV
4 days ago
Need to cancel your theory test? 📅 Find out how to cancel your DVSA theory test booking, how much notice you need to give and when you can get a refund. Read the guide 👇 https://t.co/is6ijW452F #theorytest
4 days ago
Training to become a driving instructor? 🚗📚 Prepare for ADI Part 1 with DVSA revision questions, hazard perception clips and unlimited mock tests. ADI theory test practice starts at £14.99 👇 https://t.co/f6XgdmQFxG #ADI #theorytest
5 days ago
How good are you at spotting developing hazards? 👀🚛 If you're preparing for the HGV/LGV theory test, try our FREE hazard perception practice test. Check your hazard perception skills 👇 https://t.co/NcgztXoFFJ #hgvtheorytest #hazardperception
5 days ago
Working towards your PCV theory test? 🚌 Revise with the most up-to-date DVSA practice theory test questions, hazard perception clips and unlimited PCV mock theory tests. Get 60 days' web and app access from £14.99 👇 https://t.co/DueLeoFnsn #PCV #theorytest
6 days ago
Do you recognise the mini-roundabout sign? 🔄🚗 It's a regulatory road sign that could come up in your DVSA theory test. Check its meaning and test your road sign knowledge 👇 https://t.co/TeArtP0VhE #roadsigns #theorytest
6 days ago
Preparing for LGV Driver CPC Module 2? 🚛 Our £14.99 practice package includes 60+ case studies and revision material covering the DVSA topic areas. Get ready for the case studies test 👇 https://t.co/7evNuEXTvE #drivercpc #LGV
1 week ago
Looking for free theory test practice? 📝 Try DVSA practice theory test questions for car, motorcycle, HGV/LGV, PCV or ADI Part 1. No payment or sign-up needed. Choose your practice test 👇 https://t.co/pOORgktQtG #theorytestpractice
1 week ago
Motorcycle theory test coming up? 🏍️ Revise with the latest DVSA motorcycle theory test revision questions, hazard perception practice and unlimited mock theory tests. Packages start at £5.99 for 365 days' access 👇 https://t.co/8lt9yJFTl5 #motorcycletheorytest
1 week ago
What age can you start driving in the UK? 🚗 Most people can start learning to drive a car at 17, but you can apply for a provisional licence from 15 years and 9 months. Find out more about the age rules and exceptions 👇 https://www.drivingtheory4all.co.uk/what-age-can-you-start-driving-in-the-uk #learnerdriver
1 week ago
Ready to book your theory test? 📅🚗 Choose your preferred DVSA test centre, date and time. We'll arrange your booking, subject to availability, with online and app revision included. Get your theory test booking 👇 https://www.drivingtheory4all.co.uk/book-theory-test #booktheorytest
1 week ago