There are many different approaches when it comes to breaking a horse to harness. The following describes only one way and is meant to provide general information and suggestions. There are some very good books available on the subject.

Breaking a Horse to Harness: A Step-by-Step Guide
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One of these is Breaking A Horse to Harness by Sallie Walrond (UK). This world-renowned driving expert believes that any moderate horseman can safely train a horse to drive by following her methods. This is a very informative book with clear photos and easy-to-read text.

Breaking and Training the Driving Horse: A Detailed and Comprehensive Study
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Breaking and Training the Driving Horse is written by the American driver, Doris Ganton. Ganton shows the reader how to train a green horse to drive. It includes fitting the harness, ground driving, introducing shafts and hitching to, firstly, a two-wheeled vehicle and later a four-wheeled vehicle.

 There are also several DVDs available which are easy to follow and very informative.

Long Reining to Break Horses to Harness: Training the Safe Way
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The German trainer, Heinrich Freiherr von Senden, trains professional and competitive drivers as well as breaking many horses to drive. Step by step instructions are given here from work on the single lunge, moving on to long reins, and then on to the initial hitching of the horse to the vehicle.  

A horse that is broken to harness as an ongoing operation following being broken to saddle will likely view the whole procedure as part of his education. Everything is new and different and pulling a vehicle is just another of those things. Some older horses may be too set in their ways or have preconceived ideas about what they should or shouldn't be expected to do and they may not take kindly to being expected to learn such radically different new skills. On the other hand, many horses are so trusting of their owners and so experienced with all manner of tasks that they will take kindly to their new role.

Putting a horse to a vehicle should not be taken casually. Some very nasty accidents can occur if a horse should bolt in – or half-in – a vehicle. Blinkers (blinders) are usually used on driving horses. This restricts their vision and prevents them seeing behind and perhaps panicking when this 'thing' continues to follow them. However, some carriage horses wear open bridles. If broken carefully, they will be perfectly happy with being able to see the carriage travelling behind.

 If he is used to being driven with blinkers and you wish to drive him with an open bridle, you should approach the task as if he is being broken to harness for the first time. Similarly, a horse used to an open bridle will need time to adjust to having his sight restricted with blinkers. Much depends on the horse. Any horse used to being driven in blinkers should never have the bridle removed while still attached to the carriage.

Blinkered horse
Credit: Wikimedia

Note the pull on the horse's shoulders. The heavy, strong collar is widest at the sides to spread the effort. The 'saddle' is really just a strap to keep the chains up away from the feet when the horse is not in work. There is no girth. It looks as though he has an open bridle.

Some horses just do not like being in a carriage. Some are too nervous or distrusting to ever relax fully and be trustworthy. Their wishes are probably best respected! Others will seem to have really found their niche and will be a better 'drive' than they ever were a 'ride'.

 If you've decided to use blinkers, put the driving bridle on the horse and leave him, under supervision, in the round yard for a while to get used to them. Hopefully he will be used to a crupper already. Otherwise fit this and again give him time to get used to the feel of something under his tail. Let him wander around with the harness attached. If he rounds his back and clamps his tail, the crupper will tighten and he may charge around or lash out. Let him work it out for himself. He will soon settle down.

Welsh Cob, Section D
Credit: By User:MBurger (Own work) via Wikimedia Commons

This Welsh Cob Section D is fitted with blinkers and a breastplate. The blinkers are prevented from spreading too much by straps attached to the head-piece of the bridle. The breastplate is padded. The vehicle is built specifically for combined driving events. The upward-tilting shafts allow better manoeuvrability through obstacles. The shafts are designed so that they cannot accidently come free of the tugs. During the marathon phase, the groom would stand on the step at the back.

Attach the breeching. Tie the straps to a breastplate or the girth so the breeching can't fly around if the horse panics. After a day or two, tighten the breeching a little so he gets the feel of pressure on the hindquarters.

You can lunge him with the driving gear on. If he kicks out, just keeping him going round till he is accustomed to it. Long rein him with the blinkers and remember to use voice commands. These will be especially important once you are actually driving him. If all is going well, co-opt two helpers to take a trace each and apply a little weight. A trace carrier over the loins will keep the traces up out of the way of his legs.

Attach a long, light rope to a halter under the bridle as insurance in case he takes off. It is now time to attach a light weight to the traces. Be prepared for him to flinch at new noises behind him, particularly if he can't see what is causing the noise because of the blinkers. It is a good idea to have a helper lead him for a start while you handle the long reins. Once he is happy with the situation, he can be long-reined in a number of different areas and down quiet roads, through water, etc.  Later a tyre can be attached to the traces to give him a bit more weight to pull.

The next step is to accustom him to the feel of shafts. Cut two long poles of light wood. Use a shorter rail to keep them parallel to each other. At first, attach the poles to the sides of the harness with string rather than putting the poles through the tugs. In case of an emergency, they will be more easily removed. The time spent on groundwork will never be wasted. Again long-rein him in a variety of places.

His first vehicle should not be too heavy. It should fit the horse. The shafts should be approximately horizontal to the ground when in the tugs. The cart should balance when the driver is in the seat. Too much weight on the shafts means too much weight on the horse's back. Too little weight and the cart will tip up and pull on the surcingle. If you think he might kick, a kicking strap can be attached from one shaft over his rump and attached to the other shaft. This will prevent him kicking high enough to hit the front of the cart. Some vehicles made specifically for breaking-in have extra long shafts.

Have two helpers assist you in harnessing him in for the first time. Have a helper hold him and either lead him off gently and get into the cart while he is walking or start off in the cart with a helper at his head. Stay at a walk for his first outing. The helper holds a long line attached to the halter. He can play this out and drop back behind the horse if all goes well. Have the helper assist the horse to turn by pulling gently on a shaft. Make all changes of direction large to begin with until he learns to push the shafts around.

The horse needs to hold the cart back when going downhill. Find gentle slopes at first until he becomes accustomed to 'sitting back in the breeching'. By attaching a rope to the cart and having a helper walk behind pulling on the rope, some weight can be taken off the horse until he becomes accustomed to braking the vehicle.

Four-In-Hand Put To A Brewster Drag
Credit: Wikimedia

This foun-in-hand is equipped with collars. However, these are much lighter than the collars used on draft horses engaged in heavy hauling. Only the wheelers have breeching. The leaders have trace-holders over the croup to keep the traces up. Note the driver is holding a whip.

There are varying opinions as to whether a collar or breast harness if preferable. Collars are preferred for draft horses such as Shires, Percherons and Clydesdales which need to get maximum pulling power from time to time as a horse can pull more with a collar. A collar must fit perfectly or it will quickly rub. Too small and the horse's breathing will be impaired; too large and it will rub his shoulders and make it difficult for him to pull properly. For recreational driving, it is unlikely that this effort will be needed and breast-collars are often preferred.

One breast collar will fit horses of a similar size. It must be fitted low enough to miss the windpipe but high enough so that the chest takes the weight and the horse pulls with his shoulders, not the tops of his legs! Because of the difficulty of finding well-fitting collars, breast harness has enjoyed an increase in favour.

There is much controversy as to whether the traces should be hooked up before the breeching or vice versa. Whichever way you do it probably depends on who taught or helped you when you first began driving. It is recommended that you always hold the whip. While it might seem awkward at first, it very soon becomes second nature. The whip is used as a guide not a punishment and replaces the legs of a rider. (A well-trained carriage horse will know to flex away from a light touch on the shoulder.)

Your only other aid is your voice. You may only ever need the whip in an emergency when it is imperative that the horse go forward. It won't be much good to you in the whip-holder. The whip should be long enough for the lash to reach the horse's shoulder. If you have a tandem or team, then the lash of the whip must be that much longer.

Driving a horse is great fun. It should be considered as an option for those who have enjoyed riding but have been forced to give it up for one reason or another.