Although still a comparatively rare sight, horse drawn vehicles are increasing in popularity. Perhaps surprisingly, you don't need to pass a test to drive such a vehicle on the road. However, you are obliged to adhere to the rules of the road. You should also adhere to the standards of driving and maintenance outlined in the Government's Code of Practice which outlines the minimum levels of competence required.
Consult the Code of Practice
A working group that included representatives from organisations experienced in the use of horse drawn carriages drew up the code. Knowledge of the code and adherence to it is not a legal requirement but for your own sake and the safety of other road users, it is well-worth consulting. The requirements outlined by the Code apply to all types of horse-drawn vehicles. The code was chiefly created for those who carry fare-paying passengers. If you wish to start such a business, you may have to adhere to the code and undertake the driving assessment it outlines in order to obtain a licence to operate.
The Road Driving Assessment
outlines a road driving assessment. You would need to be able to demonstrate the recommended minimum levels of competence to pass the assessment. You can apply to the or the Heavy Horse Training Committee if you wish to be assessed. There's small fee to pay but if you pass, you will be provided with a certificate of competence. They will assess your driving skills, your adherence to the rules of the road and your ability to harness and underpin. You will be observed and then asked question to test your knowledge. The British Driving Society Proficiency Test and the Heavy Horse Training Committee Road Driving Assessment test are directly accreditable.
The Highway Code
You don't have to pass a test to drive a horse and carriage on the road. However, you must adhere to the rules of the road and to adhere to those you need to read the highway code. You should read all of it but there are two sections which refer specifically to driving horses. The first of these states that you must adhere to the Code of Practice regarding the operation and maintenance of your vehicle. The other states that "All horse-drawn vehicles should have two red rear reflectors. It is safer not to drive at night but if you do, you MUST fit a light showing white to the front and red to the rear. If you drive horses on the road you have the same obligations as all other road users and the same rights. You should drive with your own safety and that of others in mind and remain courteous at all times. Your rights do not trump those of people in motor vehicles and you cannot drink and drive!