Chris As a former farm worker (25 years ago) I regularly used tractor mounted fence post drivers. I remember one in particular that was simply a massive steel hammer mounted on the tractor’s hydraulic 3-point linkage. To drive in fence posts you operated the hydraulic controls to lift the linkage up and down thus lifting the head up and then striking down onto the fence post. A six foot metal pole with a metal ring at the end was provided for the lucky assistant on the ground to try and keep the post straight! This type of post driver is still available. Thankfully, we moved onto the more controllable mast type attachment. The only moving parts in operation are the hammer which runs up and down the mast and the chain which is attached to it. The hammer is lifted up and down the mast by the chain which is connected to a hydraulic ram fed by the tractor hydraulic controls. The tractor operator controls the hammer via the hydraulic control levers in the cab. I found this link on the HSE site www.hse.gov.uk/pubns/afag104.pdf Also from memory: Most modern post “knockers” will have a gripping mechanism to hold the post straight as it is being driven into the ground, so the tractor driver is the only person who should be required at this point. But, another person is usually required to put the next post in position, and ensure it is loaded into the attachment. In my day there was no gripping mechanism so this person also had to use a long bar to keep the post straight against the mast for the first few knocks until it was firm in the ground, this might still be the case. Tractors are noisy machines so there needs to be clear hand signal communication between the two operators as they repeat the process, how often depends on the length of the fence, but it can soon reach 100 posts! Driving posts into stony dry ground will increase the risk of posts splitting and pieces flying off in every direction. Flat ground is a doddle but using a post driver on hilly, uneven ground as I did here in North Yorkshire means making adjustments to the angle of the mast or posts will not be driven in at the right angle, I think most modern implements will have hydraulic controls for this purpose. The tractor operator will spend a lot of time twisted around in his seat as he operates the post driver. Most modern tractors now have a 3 point hydraulic linkage mounted on the front, also most post driver implements can be set up to operate at right angles to the tractor so the operator has a clearer view. A competent fence contractor should be able to supply you with risk assessments and advise on any precautions your organisation will need to make. You could also ask for references from his clients regarding safe working. I hope this will be of some use.

in additon to the issues identified by geoff - don't forget to check for underground services. Death and serious injury can be caused as easily by a fence post being driven as by any other form of ground penetration. Get service drawings for utilities. Check for surface indicators, use a cat and genny, and (where necessary) hand dig / use paint.... Electricity services can kill - but telecoms (especially fibre optic) can bankrupt... And hitting a main sewage line is at best a very unpleasant experience for all involved... Steve